Data Explorer can run arbitrary SQL queries which can be costly for us if over-used. Because of that we want to add the ability to rate limit the query run endpoint, in particular when requested programmatically using API.
This commit introduces a rate limit to the `QueryController#run` endpoint. It heavily leans on the existing `RateLimiter` implementation, and the ability of `ApplicationController` to turn rate limit exceptions into nicely formatted JSON responses.
The rate limit (per 10 seconds) can be configured through the global setting `max_data_explorer_api_reqs_per_10_seconds`, and defaults to 2.
Handling can be configured through `max_data_explorer_api_req_mode`, and can be set to warn, block, or both warn and block. We will default to warn for now and monitor the logs for a while.