feat: implement Slack data source connector (#15188)

### What problem does this PR solve?

Closes #15187.

RAGFlow shipped a Slack connector
(`common/data_source/slack_connector.py`) but it was never usable:
`Slack._generate()` in the sync worker was a `pass` stub, the
connector's document-generating code was incompatible with the current
data model,
and Slack was commented out of the data-source settings UI. As a result,
teams had no way to index Slack channels/threads into a knowledge base.

This PR completes the connector end to end.

**Backend**

- `common/data_source/slack_connector.py`
- Rewrote `thread_to_doc` to produce a blob-based `Document`
(`extension`/`blob`/`size_bytes`). The previous implementation built the
doc with a `sections=[...]` argument and omitted the now-required
`blob`/`extension`/ `size_bytes` fields, so it raised a validation error
against the current `Document` model. Thread messages are now cleaned
and flattened into a single UTF-8 text blob.
- Added `load_from_state()` / `poll_source(start, end)` generators. The
connector's checkpoint interface is a no-op stub, so both full and
incremental syncs run through a single channel-iterating generator built
on the existing module helpers (`get_channels`, `filter_channels`,
`get_channel_messages`, `_process_message`), with per-channel thread
de-duplication.
- `rag/svr/sync_data_source.py`
- Implemented `Slack._generate()`. Credentials are loaded via
`StaticCredentialsProvider` (the connector requires `slack_bot_token`
and does not support `load_credentials`). Supports full reindex and
incremental polling from `poll_range_start`, plus the optional channel
filter. Modeled on the Confluence/Dropbox wrappers.
- `SlackConnector` was already exported from
`common/data_source/__init__.py`.

**Frontend (`web/`)**

- Enabled the `SLACK` data-source enum and added its form fields (Slack
bot token + optional channel filter), default values, display metadata,
and a Slack icon.
- Added `slackDescription` / `slackBotTokenTip` / `slackChannelsTip`
strings to `en.ts` and `zh.ts`.

**Tests**

- `test/unit_test/data_source/test_slack_connector_unit.py`: unit tests
covering credential loading (`load_credentials` raises,
`set_credentials_provider` initializes clients, missing credentials
raises) and document generation (standalone message + flattened thread,
blob/extension/size_bytes/metadata, and the incremental poll time
window). All 5 pass; `ruff check` is clean.

Required Slack scopes: `channels:read`, `channels:history`,
`users:read`.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

web/src/assets/svg/data-source/slack.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 122.8 122.8" width="122.8" height="122.8">
+  <path d="M25.8 77.6c0 7.1-5.8 12.9-12.9 12.9S0 84.7 0 77.6s5.8-12.9 12.9-12.9h12.9v12.9zm6.5 0c0-7.1 5.8-12.9 12.9-12.9s12.9 5.8 12.9 12.9v32.3c0 7.1-5.8 12.9-12.9 12.9s-12.9-5.8-12.9-12.9V77.6z" fill="#E01E5A"/>
+  <path d="M45.2 25.8c-7.1 0-12.9-5.8-12.9-12.9S38.1 0 45.2 0s12.9 5.8 12.9 12.9v12.9H45.2zm0 6.5c7.1 0 12.9 5.8 12.9 12.9s-5.8 12.9-12.9 12.9H12.9C5.8 58.1 0 52.3 0 45.2s5.8-12.9 12.9-12.9h32.3z" fill="#36C5F0"/>
+  <path d="M97 45.2c0-7.1 5.8-12.9 12.9-12.9s12.9 5.8 12.9 12.9-5.8 12.9-12.9 12.9H97V45.2zm-6.5 0c0 7.1-5.8 12.9-12.9 12.9s-12.9-5.8-12.9-12.9V12.9C64.7 5.8 70.5 0 77.6 0s12.9 5.8 12.9 12.9v32.3z" fill="#2EB67D"/>
+  <path d="M77.6 97c7.1 0 12.9 5.8 12.9 12.9s-5.8 12.9-12.9 12.9-12.9-5.8-12.9-12.9V97h12.9zm0-6.5c-7.1 0-12.9-5.8-12.9-12.9s5.8-12.9 12.9-12.9h32.3c7.1 0 12.9 5.8 12.9 12.9s-5.8 12.9-12.9 12.9H77.6z" fill="#ECB22E"/>
+</svg>

web/src/locales/en.ts

@@ -1238,6 +1238,12 @@ Example: Virtual Hosted Style`,
         'Upload the OAuth JSON generated from Google Console. If it only contains client credentials, run the browser-based verification once to mint long-lived refresh tokens.',
       dropboxDescription:
         'Connect your Dropbox to sync files and folders from a chosen account.',
+      slackDescription:
+        'Connect your Slack workspace to sync channel messages and threads.',
+      slackBotTokenTip:
+        'Slack bot user OAuth token (starts with xoxb-). The app needs the channels:read, channels:history, and users:read scopes.',
+      slackChannelsTip:
+        'Optional: channel names to sync (e.g., general). Leave empty to sync all accessible channels.',
       sharepointDescription:
         'Connect a SharePoint site via Microsoft Graph to sync its document libraries.',
       sharepointSiteUrlTip:

web/src/locales/zh.ts

@@ -1099,6 +1099,11 @@ NER：使用 spaCy NER 和基于规则的关键词提取来抽取实体和关系
       gmailTokenTip:
         '请上传由 Google Console 生成的 OAuth JSON。如果仅包含 client credentials，请通过浏览器授权一次以获取长期有效的刷新 Token。',
       dropboxDescription: '连接 Dropbox，同步指定账号下的文件与文件夹。',
+      slackDescription: '连接你的 Slack 工作区，同步频道消息与讨论串。',
+      slackBotTokenTip:
+        'Slack 机器人用户 OAuth Token（以 xoxb- 开头）。应用需具备 channels:read、channels:history 和 users:read 权限。',
+      slackChannelsTip:
+        '可选：需要同步的频道名称（例如 general）。留空则同步所有可访问的频道。',
       sharepointDescription: '通过 Microsoft Graph 连接 SharePoint 站点，同步其文档库。',
       sharepointSiteUrlTip:
         '要索引的 SharePoint 站点完整 URL，例如 https://contoso.sharepoint.com/sites/MySite。需要具备 Sites.Read.All 与 Files.Read.All 应用权限（管理员同意）的 Azure AD 应用。',

web/src/pages/user-setting/data-source/constant/index.tsx

@@ -43,9 +43,9 @@ export enum DataSourceKey {
   POSTGRESQL = 'postgresql',
   REST_API = 'rest_api',
   RSS = 'rss',
+  SLACK = 'slack',
   SHAREPOINT = 'sharepoint',
 
-  //   SLACK = 'slack',
   //   TEAMS = 'teams',
 }
 
@@ -130,6 +130,12 @@ export const DataSourceFeatureVisibilityMap: Partial<
   [DataSourceKey.MOODLE]: {
     syncDeletedFiles: true,
   },
+  [DataSourceKey.SLACK]: {
+    syncDeletedFiles: true,
+  },
+  [DataSourceKey.SHAREPOINT]: {
+    syncDeletedFiles: true,
+  },
   [DataSourceKey.MYSQL]: {
     syncDeletedFiles: true,
   },
@@ -213,6 +219,11 @@ export const generateDataSourceInfo = (t: TFunction) => {
       description: t(`setting.${DataSourceKey.MOODLE}Description`),
       icon: <SvgIcon name={'data-source/moodle'} width={38} />,
     },
+    [DataSourceKey.SLACK]: {
+      name: 'Slack',
+      description: t(`setting.${DataSourceKey.SLACK}Description`),
+      icon: <SvgIcon name={'data-source/slack'} width={38} />,
+    },
     [DataSourceKey.SHAREPOINT]: {
       name: 'SharePoint',
       description: t(`setting.${DataSourceKey.SHAREPOINT}Description`),
@@ -659,6 +670,22 @@ export const DataSourceFormFields = {
       required: true,
     },
   ],
+  [DataSourceKey.SLACK]: [
+    {
+      label: 'Slack Bot Token',
+      name: 'config.credentials.slack_bot_token',
+      type: FormFieldType.Password,
+      required: true,
+      tooltip: t('setting.slackBotTokenTip'),
+    },
+    {
+      label: 'Channels',
+      name: 'config.channels',
+      type: FormFieldType.Tag,
+      required: false,
+      tooltip: t('setting.slackChannelsTip'),
+    },
+  ],
   [DataSourceKey.SHAREPOINT]: [
     {
       label: 'Site URL',
@@ -1542,6 +1569,16 @@ export const DataSourceFormDefaultValues = {
       },
     },
   },
+  [DataSourceKey.SLACK]: {
+    name: '',
+    source: DataSourceKey.SLACK,
+    config: {
+      channels: [],
+      credentials: {
+        slack_bot_token: '',
+      },
+    },
+  },
   [DataSourceKey.SHAREPOINT]: {
     name: '',
     source: DataSourceKey.SHAREPOINT,