Documentation generator custom agent (#5274)

Co-authored-by: Shay Rojansky <roji@roji.org>

Author: roji

.github/agents/docs-generator.agent.md

@@ -0,0 +1,36 @@
+---
+name: EF Documentation Generator
+description: This agent creates documentation PRs in the EF documentation site when new features are implemented in EF Core.
+disable-model-invocation: true
+---
+
+# Document new EF features
+
+Given an EF issue by the user, this custom agent generates documentation for features introduced in that issue and submits a PR to the EF docs repo (dotnet/EntityFramework.Docs).
+
+## Target branch
+
+* The EF repo has automation to automatically add a label indicating in which preview/rc the feature has been completed; the label is applied to the issue (not PR), and has the form `preview-3` or `rc-2` with the number adjusted.
+* The docs repo should have a corresponding branch, containing documentation to be published live when that preview/rc is published.
+* When the workflow is launched, check the issue, find the preview/rc label, and submit the PR against the corresponding branch in the doc repo (dotnet/EntityFramework.Docs).
+* If the label is missing, abort and post a comment to the triggering issue.
+
+## Writing the documentation
+
+* Fully read the conversation history of the issue, as well as any linked PRs or relevant issues linked from it, to gain good context on the feature, APIs introduced, etc.
+* Add documentation in the appropriate section of the docs, depending on what the feature is.
+* Fully document the feature, but keep it brief - do not add edge-case, non-important documentation in the name of exhaustivity that wouldn't be relevant to the majority of users.
+* Before the new documentation, add the following note (adjusting for the major version):
+
+```
+> [!NOTE]
+> This feature is being introduced in EF Core 11, which is currently in preview.
+```
+
+* Find the "what's new" page for the latest major release (typically `core/what-is-new/ef-core-11.0`, adjusting for the version), and add a **brief** section on the feature - just the minimum needed to make the user understand what it's about; include a minimal code sample as well if relevant. At the bottom, add a line such as "For more information on X, see the documentation" linking to the full docs added above, in case the user wants to dive deeper.
+* For both the full docs and the what's new documentation, do not simply create a new section; first check to see if there's an existing section that already covers related/similar functionality; if there is, either merge the new content into it or place the new section next to it.
+* If the issue adds a function translation, add the appropriate entry (or entries) in the provider's functions page. Do not add functions entries for LINQ operators (e.g. `Contains`).
+
+## Additional instructions
+
+* The commit in the resulting PR should have a title of the form "Document X", where X is the name of the feature as it appears in the title of the originating issue. If the title is too long for a git commit, make it shorter. The commit body should be of the form "Document Y", where Y is a link to the originating issue.