User-defined process parameters are recursively defined

[m-mohr]

The user-defined process parameters are recursively defined, which is not correct. It shouldn't be recursive.

See OpenAPI doc -> /processes -> processes -> parameters -> schema -> parameters

Also, return values and service type parameters show the "parameters" json schema keyword, which doesn't make sense there.

[m-mohr]

Commit 7ed8714 tries to fix this, but another issue in Redoc prevents correct rendering: Redocly/redoc#1154

Also, I'm not sure it's worth the additional complexity in the schemas.