Include file extension checks in attachment API (#32151)

From testing, I found that issue posters and users with repository write
access are able to edit attachment names in a way that circumvents the
instance-level file extension restrictions using the edit attachment
APIs. This snapshot adds checks for these endpoints.

templates/swagger/v1_json.tmpl

@@ -7706,6 +7706,9 @@
           "404": {
             "$ref": "#/responses/error"
           },
+          "422": {
+            "$ref": "#/responses/validationError"
+          },
           "423": {
             "$ref": "#/responses/repoArchivedError"
           }
@@ -8328,6 +8331,9 @@
           "404": {
             "$ref": "#/responses/error"
           },
+          "422": {
+            "$ref": "#/responses/validationError"
+          },
           "423": {
             "$ref": "#/responses/repoArchivedError"
           }
@@ -13474,6 +13480,9 @@
           },
           "404": {
             "$ref": "#/responses/notFound"
+          },
+          "422": {
+            "$ref": "#/responses/validationError"
           }
         }
       }