developers/design: Add internal lib-http response codes

Author: sirainen

docs/developers/design/http.md

@@ -0,0 +1,25 @@
+---
+layout: doc
+title: lib-http
+dovecotlinks:
+  lib_http: lib-http
+  lib_http_response_codes:
+    hash: internal-http-response-codes
+    text: "Dovecot HTTP Internal Response Codes"
+---
+
+# lib-http
+
+## Internal HTTP Response Codes
+
+| Number | Code | Description |
+| ------ | ---- | ----------- |
+| 9000 | ABORTED | The request was aborted. |
+| 9001 | INVALID_URL | Failed to parse HTTP target url. |
+| 9002 | HOST_LOOKUP_FAILED | Failed to perform DNS lookup for the host. |
+| 9003 | CONNECT_FAILED | Failed to setup any connection for the host and client settings allowed no more attempts. |
+| 9004 | INVALID_REDIRECT | Service returned an invalid redirect response for this request. |
+| 9005 | CONNECTION_LOST | The connection was lost unexpectedly while handling the request and client settings allowed no more attempts. |
+| 9006 | BROKEN_PAYLOAD | The input stream passed to the request using http_client_request_set_payload() returned an error while sending the request. |
+| 9007 | BAD_RESPONSE | The service returned a bad response. |
+| 9008 | TIMED_OUT | The request timed out (either this was the last attempt or the absolute timeout was hit). |