Provide higher-level client UI

[forman]

Is your feature request related to a problem? Please describe.

The current cuiman client API (and CLI, GUI) are rather low level - an almost 1:1 translation of the OGC API – Processes protocol.

In addition, the OGC API – Processes is an execution API, not a negotiation protocol, neither it is a UI contract. Therefore:

1. Client users have to query the execution status of the jobs. This is tedious and prone to errors.
2. the generated outputs formats and transmission modes are highly server- and application-specific. External info must be available (demos, docs) to use it correctly. It is therefore very important and desirable to provide users with means to access to generated results in an application-specific way.

Describe the solution you'd like

Provide a higher level API comprising at least

1. an async execute function that resolves as soon as the job finishes;
2. application-specific access function(s) to access the results and work with it, e.g., in Jupyter notebooks.