Refine docstrings and API of BayesianSolver

[AlessandroPierro]

Objective of issue: improve docstrings and API in Bayesian Solver

I'm submitting a ...

• [x] feature request
• [x] documentation request

Additional Information

• The API of the Bayesian solver should be refined to reduce the use of dictionaries, preferring something like enums
• The docstrings should be updated to include details on such arguments