refact: openapi splitted into separate files

api/paths/titles-id.yaml

@@ -0,0 +1,29 @@
+get:
+  summary: Get title description
+  parameters:
+    - in: path
+      name: title_id
+      required: true
+      schema:
+        type: integer
+        format: int64
+    - in: query
+      name: fields
+      schema:
+        type: string
+        default: all
+  responses:
+    '200':
+      description: Title description
+      content:
+        application/json:
+          schema:
+            $ref: "../schemas/Title.yaml"
+    '404':
+      description: Title not found
+    '400':
+      description: Request params are not correct
+    '500':
+      description: Unknown server error
+    '204':
+      description: No title found