Pull request: home: improve mobileconfig http api

Merge in DNS/adguard-home from 2358-mobileconfig to master

Updates #2358.

Squashed commit of the following:

commit ab3c7a75ae21f6978904f2dc237cb84cbedff7ab
Merge: fa002e400 b4a35fa88
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Nov 25 16:11:06 2020 +0300

    Merge branch 'master' into 2358-mobileconfig

commit fa002e40004656db08d32c926892c6c820fb1338
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Nov 25 15:19:00 2020 +0300

    home: improve mobileconfig http api

openapi/openapi.yaml

@@ -959,27 +959,61 @@
             'application/json':
               'schema':
                 '$ref': '#/components/schemas/ProfileInfo'
+
   '/apple/doh.mobileconfig':
     'get':
-      'tags':
-      - 'mobileconfig'
-      - 'global'
       'operationId': 'mobileConfigDoH'
-      'summary': 'Get DNS over HTTPS .mobileconfig'
+      'parameters':
+      - 'description': >
+          Host for which the config is generated.  If no host is provided,
+          `tls.server_name` from the configuration file is used.  If
+          `tls.server_name` is not set, the API returns an error with a 500
+          status.
+        'example': 'example.org'
+        'in': 'query'
+        'name': 'host'
+        'schema':
+          'type': 'string'
       'responses':
         '200':
-          'description': 'DNS over HTTPS plist file'
-
-  '/apple/dot.mobileconfig':
-    'get':
+          'description': 'DNS over HTTPS plist file.'
+        '500':
+          'content':
+            'application/json':
+              'schema':
+                '$ref': '#/components/schemas/Error'
+          'description': 'Server configuration error.'
+      'summary': 'Get DNS over HTTPS .mobileconfig.'
       'tags':
       - 'mobileconfig'
       - 'global'
+  '/apple/dot.mobileconfig':
+    'get':
       'operationId': 'mobileConfigDoT'
-      'summary': 'Get TLS over TLS .mobileconfig'
+      'parameters':
+      - 'description': >
+          Host for which the config is generated.  If no host is provided,
+          `tls.server_name` from the configuration file is used.  If
+          `tls.server_name` is not set, the API returns an error with a 500
+          status.
+        'example': 'example.org'
+        'in': 'query'
+        'name': 'host'
+        'schema':
+          'type': 'string'
       'responses':
         '200':
           'description': 'DNS over TLS plist file'
+        '500':
+          'content':
+            'application/json':
+              'schema':
+                '$ref': '#/components/schemas/Error'
+          'description': 'Server configuration error.'
+      'summary': 'Get DNS over TLS .mobileconfig.'
+      'tags':
+      - 'mobileconfig'
+      - 'global'
 
 'components':
   'requestBodies':