chore(librarian): onboard to librarian (#197)

* feat: onboard google-auth-httplib2 to librarian

* update changelog

* update version

Author: ohmayr

.github/.OwlBot.lock.yaml

@@ -0,0 +1,6 @@
+global_files_allowlist:
+  # Allow the container to read and write the root `CHANGELOG.md`
+  # file during the `release` step to update the latest client library
+  # versions which are hardcoded in the file.
+  - path: "CHANGELOG.md"
+    permissions: "read-write"

.github/.OwlBot.yaml

@@ -0,0 +1,10 @@
+image: us-central1-docker.pkg.dev/cloud-sdk-librarian-prod/images-prod/python-librarian-generator:latest
+libraries:
+  - id: google-auth-httplib2
+    version: 0.2.1
+    apis: []
+    source_roots:
+      - .
+    preserve_regex: []
+    remove_regex: []
+    tag_format: v{version}

.github/release-please.yml

@@ -1,5 +1,7 @@
 # Changelog
 
+[1]: https://pypi.org/project/google-auth-httplib2/#history
+
 ## [0.2.1](https://github.com/googleapis/google-auth-library-python-httplib2/compare/v0.2.0...v0.2.1) (2025-10-30)