Use enum for WPS dialects

[MichaelLangbein]

As discussed here

Citing:

I think it might be better to introduce a enumeration for WPS dialects.
Though, I think you can merge this in order to resolve the issue.

Code here

data class WPSConfiguration(val wpsURL: String, val process: String, val wpsVersion : String, val dialect: String, val retryConfiguration: RetryConfiguration)