add x-request-id support for debug rest-api queries

[mesilov]

Add an option to set the x-request-id header for debug problem rest-api queries

Request-Id, it's uniquely identifies every HTTP request involved in operation processing, and is generated on the caller side and passed to callee.

Requirements

1. Autogenerate x-request-id if not set
2. pass exists x-request-id from different sources: http-query, call args, etc
3. write x-request-id to existing logs
4. add x-request-id to the response meta information

Example

Default flow

1. The user clicks on a button in the Bitrix24 application
2. Browser send request to server
3. The server creates a unique x-request-id key and adds it to request headers
4. The PHP application calls bitrix24-php-sdk and try to request bitrix24 rest-api
5. SDK find exists x-request-id key and add this key to request headers
6. Bitrix24 API-GATEWAY finds x-request-id key and writes it in his logs
7. Bitrix24 send response to bitrix24-php-sdk
8. bitrix24-php-sdk sign response with this x-request-id key and write it to logs

If a developer needs to investigate some problems in rest-api calls they can send x-request-id key to bitrix24 support and they try to find his request

Default fields in $_SERVER to pass exists request id into sdk

• HTTP_X_REQUEST_ID
• UNIQUE_ID

Server configuration

• nginx http://nginx.org/en/docs/http/ngx_http_core_module.html#var_request_id