Add "EXTERNAL_DEBUG_URL" environment variable

[AndrewDryga]

It should contain pattern that will be applied as link (if present) on details tab. Value should have a placeholder that will be replaced by request_id.

Link should say "Find in external debugger".

[alexeybondarenko]

As I've understood @AndrewDryga we need to add a new link Open in Debugger next to Copy CURL. A debugger is an external system. A link on debugger could be is specifying in EXTERNAL_DEBUG_URL. eg. https://example.com/{request_id}/logs. UI need to replace {request_id} with request_id of request.