Scenario:
Try to use swagger editor to query for multiple key ids for process definitions.

Current request resolves to:
http://localhost:8080/engine-rest/process-definition?keysIn=key1&keysIn=key2
Expected:
http://localhost:8080/engine-rest/process-definition?keysIn=key1,key2 - comma separated string list

AT:

• change `array` type of all query parameter to `string`
• extend the descriptions if needed with "a comma-separated list of..."