OAPI: add sections to OpenAPI paths

This just makes the grouping a bit more obvious. It follows the already
available tags.

pkg/api/flamenco-manager.yaml

@@ -12,6 +12,8 @@ info:
 servers:
   - url: /
 paths:
+  ## Meta
+
   /api/version:
     summary: Clients can use this to check this is actually a Flamenco server.
     get:
@@ -39,6 +41,8 @@ paths:
             application/json:
               schema: {$ref: "#/components/schemas/ManagerConfiguration"}
 
+  ## Worker
+
   /api/worker/register-worker:
     summary: Registration of new workers
     post:
@@ -217,6 +221,8 @@ paths:
               schema:
                 $ref: '#/components/schemas/Error'
 
+  ## Jobs
+
   /api/jobs/types:
     summary: Available Flamenco job types.
     get:
@@ -280,7 +286,6 @@ paths:
             application/json:
               schema: {$ref: "#/components/schemas/Error"}
 
-
   /api/jobs/{job_id}:
     summary: Job info and management
     get:
@@ -299,6 +304,8 @@ paths:
             application/json:
               schema: {$ref: "#/components/schemas/Job"}
 
+  ## Shaman
+
   /shaman/checkout/requirements:
     summary: Allows a client to check which files are available on the server, and which ones are still unknown.
     post: