swagger: update semantic errors

api/swagger.yaml

@@ -94,10 +94,16 @@ paths:
                 $ref: '#/components/schemas/User'
 
   /users/{username}/posts:
-    get:
+    post:
       tags:
         - User Endpoints
         - Posts Endpoints
+      parameters:
+        - name: username
+          required: true
+          in: path
+          schema:
+            type: string
       summary: Get the list of posts a user has created/submitted.
       requestBody:
         $ref: '#/components/requestBodies/Listing'
@@ -118,10 +124,16 @@ paths:
           $ref: '#/components/responses/ServerError'
 
   /users/{username}/comments:
-    get:
+    post:
       tags:
         - User Endpoints
         - Comments Endpoints
+      parameters:
+        - name: username
+          required: true
+          in: path
+          schema:
+            type: string
       summary: Get the list of comments a user has submitted.
       requestBody:
         $ref: '#/components/requestBodies/Listing'