feat(server): add search docs by keyword gql api (#12866)

close AI-220









#### PR Dependency Tree


* **PR #12866** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **New Features**
- Introduced a new document search capability, allowing users to search
for documents by keyword within a workspace.
- Search results include document details such as title, highlights,
creation and update timestamps, and creator/updater information.
  - Added support for limiting the number of search results returned.
- **Tests**
- Added comprehensive end-to-end and snapshot tests to ensure accuracy
and access control for the new search functionality.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/schema.gql

@@ -1502,6 +1502,24 @@ type SameSubscriptionRecurringDataType {
   recurring: String!
 }
 
+type SearchDocObjectType {
+  blockId: String!
+  createdAt: DateTime!
+  createdByUser: PublicUserType
+  docId: String!
+  highlight: String!
+  title: String!
+  updatedAt: DateTime!
+  updatedByUser: PublicUserType
+}
+
+input SearchDocsInput {
+  keyword: String!
+
+  """Limit the number of docs to return, default is 20"""
+  limit: Int
+}
+
 input SearchHighlight {
   before: String!
   end: String!
@@ -2074,6 +2092,9 @@ type WorkspaceType {
   """Search a specific table"""
   search(input: SearchInput!): SearchResultObjectType!
 
+  """Search docs by keyword"""
+  searchDocs(input: SearchDocsInput!): [SearchDocObjectType!]!
+
   """The team subscription of the workspace, if exists."""
   subscription: SubscriptionType