Improvement in error response /v1/crowdactions/slug/{slug} and /v1/crowdactions/{id}

[dromerolovo]

Regarding /v1/crowdactions/slug/{slug} endpoint:

When requesting a crowdaction by a slug that doesn't exist, there is a mismatch in the response between the Status of the response: 500 and the statusCode of the response body "statusCode": 400 could be confusing for the client. Would be better if both are 404 Not Found.

Regarding /v1/crowdactions/{id} endpoint:

When requesting a crowdaction by an id that doesn't exist, the Status of the response is 500. Would be more convenient if the response is 404 Not Found.