Remoulade

What's Changed
* fix(apispec): validate only if request is actually json and not empty. by desaintmartin in https://github.com/wiremind/remoulade/pull/287
* fix(tests): test_rabbitmq_cli: use test rabbitmq_broker instead of real rabbitmq broker.

**Full Changelog**: https://github.com/wiremind/remoulade/compare/v0.46.0...v0.46.1

What's Changed
Changed
* Test python 3.10 and improve linters.
* Remove deprectaed python 3.6 syntax.

Added
* Services: rabbitmq, redis, postgresql URL can be specified through env vars.
* Add dockerfile for composition example and auto build it.

**Full Changelog**: https://github.com/wiremind/remoulade/compare/v0.45.0...v0.46.0