feat: use another schema for poll creation

This is an attempt at handling the requirements

openapi/components/schemas/poll-new.yaml

@@ -0,0 +1,8 @@
+type: object
+description:
+  $ref: 'poll.md'
+properties:
+  $ref: 'poll-properties.yaml'
+required:
+  - subject
+  - proposals

openapi/components/schemas/poll.yaml

@@ -3,6 +3,3 @@ description:
   $ref: 'poll.md'
 properties:
   $ref: 'poll-properties.yaml'
-required:
-  - title
-  - proposals

openapi/paths/polls.yaml

@@ -18,7 +18,7 @@ post:
     content:
       application/json:
         schema:
-          $ref: ../components/schemas/poll.yaml
+          $ref: ../components/schemas/poll-new.yaml
   responses:
     '201':
       description: Created