Add language statistics API endpoint (#11737)

* Add language statistics API

* Add tests

templates/swagger/v1_json.tmpl

@@ -6049,6 +6049,42 @@
         }
       }
     },
+    "/repos/{owner}/{repo}/languages": {
+      "get": {
+        "produces": [
+          "application/json"
+        ],
+        "tags": [
+          "repository"
+        ],
+        "summary": "Get languages and number of bytes of code written",
+        "operationId": "repoGetLanguages",
+        "parameters": [
+          {
+            "type": "string",
+            "description": "owner of the repo",
+            "name": "owner",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "string",
+            "description": "name of the repo",
+            "name": "repo",
+            "in": "path",
+            "required": true
+          }
+        ],
+        "responses": {
+          "200": {
+            "$ref": "#/responses/LanguageStatistics"
+          },
+          "404": {
+            "$ref": "#/responses/notFound"
+          }
+        }
+      }
+    },
     "/repos/{owner}/{repo}/milestones": {
       "get": {
         "produces": [
@@ -14917,6 +14953,16 @@
         }
       }
     },
+    "LanguageStatistics": {
+      "description": "LanguageStatistics",
+      "schema": {
+        "type": "object",
+        "additionalProperties": {
+          "type": "integer",
+          "format": "int64"
+        }
+      }
+    },
     "MarkdownRender": {
       "description": "MarkdownRender is a rendered markdown document",
       "schema": {