feat(api): add sort parameter to list issues API (#7211)

- Add the `sort` parameter to the `/api/v1/{repo}/{owner}/issues` API endpoint. Default behavior is preserved.
- Resolves forgejo/forgejo#4173
- Add (non-exhaustive) integration testing.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7211
Reviewed-by: Otto <otto@codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

templates/swagger/v1_json.tmpl

@@ -8628,6 +8628,24 @@
             "description": "page size of results",
             "name": "limit",
             "in": "query"
+          },
+          {
+            "enum": [
+              "relevance",
+              "latest",
+              "oldest",
+              "recentupdate",
+              "leastupdate",
+              "mostcomment",
+              "leastcomment",
+              "nearduedate",
+              "farduedate"
+            ],
+            "type": "string",
+            "default": "latest",
+            "description": "Type of sort",
+            "name": "sort",
+            "in": "query"
           }
         ],
         "responses": {