Closes#14768
### What problem does this PR solve?
The `list_chats` and `list_searches` REST API endpoints did not enforce
authorization on the `owner_ids` query parameter. Any authenticated user
could pass arbitrary tenant IDs to `owner_ids` and retrieve chats or
search apps belonging to other tenants they are not a member of.
This PR resolves the issue by:
1. Looking up the current user's authorized tenants via
`TenantService.get_joined_tenants_by_user_id` and rejecting any
`owner_ids` that fall outside that set.
2. When no `owner_ids` are provided, scoping the query to only the
user's authorized tenants instead of returning an unfiltered result.
3. Adding unit tests that verify unauthorized `owner_ids` are rejected
with `OPERATING_ERROR`.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### What problem does this PR solve?
Refactor /api/v1/chats to be more RESTful.
### Type of change
- [x] Refactoring
---------
Co-authored-by: Jin Hai <haijin.chn@gmail.com>
### What problem does this PR solve?
Searches /search API to RESTFul
### Type of change
- [x] Documentation Update
- [x] Refactoring
Co-authored-by: Jin Hai <haijin.chn@gmail.com>
Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>
