Fix JSON schema to issues in issue board lists

spec/fixtures/api/schemas/issue.json

@@ -10,7 +10,9 @@
     "title": { "type": "string" },
     "confidential": { "type": "boolean" },
     "labels": {
-      "type": ["array"],
+      "type": "array",
+      "items": {
+        "type": "object",
         "required": [
           "id",
           "color",
@@ -25,8 +27,14 @@
             "pattern": "^#[0-9A-Fa-f]{3}{1,2}+$"
           },
           "description": { "type": ["string", "null"] },
+          "text_color": {
+            "type": "string",
+            "pattern": "^#[0-9A-Fa-f]{3}{1,2}+$"
+          },
           "title": { "type": "string" },
           "priority": { "type": ["integer", "null"] }
+        },
+        "additionalProperties": false
       }
     },
     "assignee": {