Merge branch 'issue-boards-label-text-color' into 'master'

Added text color to issues labels in issue board lists

## What does this MR do?

Adds the text color for labels in the response. The frontend was
already setup to handle this, just needed the data from the backend.

See merge request !5898

app/assets/javascripts/boards/models/label.js.es6

@@ -3,6 +3,7 @@ class ListLabel {
     this.id = obj.id;
     this.title = obj.title;
     this.color = obj.color;
+    this.textColor = obj.text_color;
     this.description = obj.description;
     this.priority = (obj.priority !== null) ? obj.priority : Infinity;
   }

app/controllers/projects/boards/issues_controller.rb

@@ -12,7 +12,7 @@ module Projects
           only: [:iid, :title, :confidential],
           include: {
             assignee: { only: [:id, :name, :username], methods: [:avatar_url] },
-            labels:   { only: [:id, :title, :description, :color, :priority] }
+            labels:   { only: [:id, :title, :description, :color, :priority], methods: [:text_color] }
           })
       end
 

spec/fixtures/api/schemas/issue.json

@@ -10,23 +10,31 @@
     "title": { "type": "string" },
     "confidential": { "type": "boolean" },
     "labels": {
-      "type": ["array"],
-      "required": [
-        "id",
-        "color",
-        "description",
-        "title",
-        "priority"
-      ],
-      "properties": {
-        "id": { "type": "integer" },
-        "color": {
-          "type": "string",
-          "pattern": "^#[0-9A-Fa-f]{3}{1,2}+$"
+      "type": "array",
+      "items": {
+        "type": "object",
+        "required": [
+          "id",
+          "color",
+          "description",
+          "title",
+          "priority"
+        ],
+        "properties": {
+          "id": { "type": "integer" },
+          "color": {
+            "type": "string",
+            "pattern": "^#[0-9A-Fa-f]{3}{1,2}+$"
+          },
+          "description": { "type": ["string", "null"] },
+          "text_color": {
+            "type": "string",
+            "pattern": "^#[0-9A-Fa-f]{3}{1,2}+$"
+          },
+          "title": { "type": "string" },
+          "priority": { "type": ["integer", "null"] }
         },
-        "description": { "type": ["string", "null"] },
-        "title": { "type": "string" },
-        "priority": { "type": ["integer", "null"] }
+        "additionalProperties": false
       }
     },
     "assignee": {