GRM-20: refactor(scripts): centralize constants, API clients, and HTTP status codes

- Add shared config.py with API URLs, regexes, timeouts, pagination
- Add GiteaClient and VikunjaClient in api_clients.py with pooled sessions
- Add APIError exception for unified HTTP error handling
- Refactor all scripts to use shared modules and http.HTTPStatus
- Rewrite unit tests to mock clients and use HTTPStatus constants
- Add tests for api_clients and config modules
- Achieve 100% test coverage

tests/unit/test_auto_merge.py

@@ -1,21 +1,15 @@
 """Unit tests for scripts/auto_merge.py."""
 
+import http
 from unittest.mock import MagicMock, patch
 
 import click
 import pytest
-import requests
 from click.testing import CliRunner
 
-from scripts.auto_merge import (
-    CONVENTIONAL_RE,
-    GITEA_API,
-    TASK_ID_RE,
-    extract_task_id,
-    main,
-    merge_pr,
-    validate_pr_title,
-)
+from gitea_runner_manager.config import CONVENTIONAL_RE, TASK_ID_RE
+from gitea_runner_manager.exceptions import APIError
+from scripts.auto_merge import extract_task_id, main, validate_pr_title
 
 
 class TestRegexes:
@@ -59,32 +53,12 @@ class TestValidatePrTitle:
         assert "conventional" in str(exc.value)
 
 
-class TestMergePr:
-    @patch("scripts.auto_merge.requests.post")
-    def test_successful_merge(self, mock_post: MagicMock) -> None:
-        mock_response = MagicMock()
-        mock_post.return_value = mock_response
-        merge_pr("tok", "owner/repo", "7", "GRM-19: fix: bug")
-        mock_post.assert_called_once()
-        args, kwargs = mock_post.call_args
-        assert kwargs["headers"]["Authorization"] == "token tok"
-        assert kwargs["json"]["Do"] == "squash"
-        assert kwargs["json"]["MergeTitleField"] == "GRM-19: fix: bug"
-        assert GITEA_API in args[0]
-
-    @patch("scripts.auto_merge.requests.post")
-    def test_merge_raises_on_http_error(self, mock_post: MagicMock) -> None:
-        mock_response = MagicMock()
-        mock_response.raise_for_status.side_effect = requests.HTTPError("500")
-        mock_post.return_value = mock_response
-        with pytest.raises(requests.HTTPError):
-            merge_pr("tok", "owner/repo", "7", "title")
-
-
 class TestMain:
     @patch.dict("os.environ", {"GITEA_TOKEN": "tok"})
-    @patch("scripts.auto_merge.merge_pr")
-    def test_successful_flow(self, mock_merge: MagicMock) -> None:
+    @patch("scripts.auto_merge.GiteaClient")
+    def test_successful_flow(self, mock_client_cls: MagicMock) -> None:
+        mock_client = MagicMock()
+        mock_client_cls.return_value = mock_client
         runner = CliRunner()
         result = runner.invoke(
             main,
@@ -92,7 +66,8 @@ class TestMain:
         )
         assert result.exit_code == 0
         assert "squash-merged" in result.output
-        mock_merge.assert_called_once_with("tok", "owner/repo", "7", "GRM-19: fix: resolve timeout")
+        mock_client_cls.assert_called_once()
+        mock_client.merge_pr.assert_called_once_with("7", "GRM-19: fix: resolve timeout")
 
     @patch.dict("os.environ", {"GITEA_TOKEN": ""}, clear=True)
     def test_missing_token_exits(self) -> None:
@@ -116,23 +91,23 @@ class TestMain:
         assert "conventional" in result.output
 
     @patch.dict("os.environ", {"GITEA_TOKEN": "tok"})
-    @patch("scripts.auto_merge.merge_pr")
-    def test_merge_pr_failure_raises_click(self, mock_merge: MagicMock) -> None:
-        mock_merge.side_effect = requests.HTTPError("500")
+    @patch("scripts.auto_merge.GiteaClient")
+    def test_merge_pr_failure_raises_click(self, mock_client_cls: MagicMock) -> None:
+        mock_client = MagicMock()
+        mock_client.merge_pr.side_effect = APIError(http.HTTPStatus.INTERNAL_SERVER_ERROR, "server error")
+        mock_client_cls.return_value = mock_client
         runner = CliRunner()
-        result = runner.invoke(main, ["GRM-19-fix", "fix: bug", "repo", "1"])
+        result = runner.invoke(main, ["GRM-19-fix", "fix: bug", "owner/repo", "1"])
         assert result.exit_code == 1
         assert "HTTP" in result.output
 
     @patch.dict("os.environ", {"GITEA_TOKEN": "tok"})
-    @patch("scripts.auto_merge.merge_pr")
-    def test_merge_pr_json_parse_failure(self, mock_merge: MagicMock) -> None:
-        mock_response = MagicMock()
-        mock_response.status_code = 502
-        mock_response.json.side_effect = ValueError("not json")
-        err = requests.HTTPError("502", response=mock_response)
-        mock_merge.side_effect = err
+    @patch("scripts.auto_merge.GiteaClient")
+    def test_merge_pr_json_parse_failure(self, mock_client_cls: MagicMock) -> None:
+        mock_client = MagicMock()
+        mock_client.merge_pr.side_effect = APIError(http.HTTPStatus.BAD_GATEWAY, "bad gateway")
+        mock_client_cls.return_value = mock_client
         runner = CliRunner()
-        result = runner.invoke(main, ["GRM-19-fix", "fix: bug", "repo", "1"])
+        result = runner.invoke(main, ["GRM-19-fix", "fix: bug", "owner/repo", "1"])
         assert result.exit_code == 1
-        assert "502" in result.output
+        assert str(http.HTTPStatus.BAD_GATEWAY) in result.output