output: http: document 'allow_duplicated_headers' option

Signed-off-by: Eduardo Silva <[email protected]>

Author: edsiper

pipeline/outputs/http.md

@@ -6,16 +6,17 @@ The **http** output plugin allows to flush your records into a HTTP endpoint. Fo
 
 | Key | Description | default |
 | :--- | :--- | :--- |
-| Host | IP address or hostname of the target HTTP Server | 127.0.0.1 |
-| HTTP\_User | Basic Auth Username |  |
-| HTTP\_Passwd | Basic Auth Password. Requires HTTP\_User to be set |  |
-| Port | TCP port of the target HTTP Server | 80 |
+| host | IP address or hostname of the target HTTP Server | 127.0.0.1 |
+| http\_User | Basic Auth Username |  |
+| http\_Passwd | Basic Auth Password. Requires HTTP\_User to be set |  |
+| port | TCP port of the target HTTP Server | 80 |
 | Proxy | Specify an HTTP Proxy. The expected format of this value is [http://host:port](http://host:port). Note that _https_ is **not** supported yet. |  |
-| URI | Specify an optional HTTP URI for the target web server, e.g: /something | / |
-| Compress | Set payload compression mechanism. Option available is 'gzip' | |
-| Format | Specify the data format to be used in the HTTP request body, by default it uses _msgpack_. Other supported formats are _json_, _json\_stream_ and _json\_lines_ and _gelf_. | msgpack |
+| uri | Specify an optional HTTP URI for the target web server, e.g: /something | / |
+| compress | Set payload compression mechanism. Option available is 'gzip' | |
+| format | Specify the data format to be used in the HTTP request body, by default it uses _msgpack_. Other supported formats are _json_, _json\_stream_ and _json\_lines_ and _gelf_. | msgpack |
+| allow\_duplicated\_headers | Specify if duplicated headers are allowed. If a duplicated header is found, the latest key/value set is preserved. | true |
 | header\_tag | Specify an optional HTTP header field for the original message tag. |  |
-| Header | Add a HTTP header key/value pair. Multiple headers can be set. |  |
+| header | Add a HTTP header key/value pair. Multiple headers can be set. |  |
 | json\_date\_key | Specify the name of the date field in output | date |
 | json\_date\_format | Specify the format of the date. Supported formats are _double_ and _iso8601_ \(eg: _2018-05-30T09:39:52.000681Z_\) | double |
 | gelf\_timestamp\_key | Specify the key to use for `timestamp` in _gelf_ format |  |