Add API endpoint to check staff application availability and enforce open/close periods

open_api/src/main/resources/schemas/forms/staff_apply/staff_apply.yml

@@ -24,6 +24,28 @@ StaffApply:
           application/json:
             schema:
               $ref: '../../generic/errors.yml#/components/schemas/ApiError'
+StaffApplicationsIsOpen:
+  get:
+    tags:
+      - applications
+    summary: Get if staff applications are open
+    description: Get if staff applications are open
+    operationId: getStaffApplicationsIsOpen
+    responses:
+      '200':
+        description: If staff applications are open
+        content:
+          application/json:
+            schema:
+              type: boolean
+      '403':
+        description: If staff applications are not open
+      default:
+        description: Unexpected error
+        content:
+          application/json:
+            schema:
+              $ref: '../../generic/errors.yml#/components/schemas/ApiError'
 components:
   schemas:
     StaffApplication: