[ROO-2237] Adding PROXY_TIMEOUT as an optional parameter to configure a custom timeout

* PROD-1889 adding nginx status so this could be consumed by DataDog

* PROD-1889 bumping version

* PROD-1889 adding env variables to customize the status page

* PROD-1889 updating CHANGELOG

* PROD-1889 updating docs

* PROD-1889 more doc updates

Bump CircleCI setup_remote_docker and add Authentication using org-global context

Increase the size of the buffer that stores the response headers to 8K

https://nginx.org/en/docs/http/ngx_http_upstream_module.html#var_upstream_status

Add `--fail` to the curl command to catch app 500 erros

Use `$request_method` and `$request_uri`

Otherwise, DD parses `path=GET`, treating the space as a separator.

Add request duration to the nginx log format

Bump to 0.3.1

- log `$request_time`; request processing time in seconds (millisecond resolution).
- stop logging unusable information, e.g. private remote ips, proxy path information.

Update CHANGELOG.md wit 0.2.2 and 0.3.0 changes

Allow client_body_buffer_size to be overriden.

This change allows `client_body_buffer_size` to be overriden by users of
the sidecar. It defaults the environment variable to 8k, which is what
nginx sets it to on x86-64.

We're regularly seeing larger requests get written to disk on some of
our services. This will allow us to configure a larger buffer size to
avoid this.

In the future, we may want to change the default 8k size to something
larger.

Add --max-time to the curl health check.

We're seeing the application accept connections but then hang. This
changes the curl command to time out the request after 5s (default ECS
health check timeout) which will cause it to retry.

It's unclear whether this is a debugging step or a workaround. Will test
in staging initially.

Wait for the application to pass healthchecks

Pass X-Forwarded-Proto

Rack::Protection::HttpOrigin is checking if the origin url (including the scheme) matches base url

https://github.com/sinatra/sinatra/blob/b801c6b76b89eb071e2b01700273054bbe8aae05/rack-protection/lib/rack/protection/http_origin.rb#L33

UI-XX: Set host header on proxy to request host