Refactor oauth2 Experiment module Implementation

[freizl]

Changes

• Remove data type GrantTypeFlow, rather make concret type for each grant type.
  See hoauth2/src/Network/OAuth2/Experiment/GrantType/ folder.

• Split type class for each flow into its own file and simplify the instance implementation a little bit.
  See hoauth2/src/Network/OAuth2/Experiment/Flows folder

  • The type class is responsible for translate different GrantType Application into flow request body
  • There are separated ConduitXXXRequest stitch them together.

• Separate IDP from Application.

• IdpApplication is common data type instead of data family, which stiches IDP and grant type Applications.

Notes

The impact to user who are using hoauth2-provider package seems minimal.
See this diff for reference. (Changes to hoauth2-providers-tutorial/src/HOAuth2ProvidersTutorial.hs file)

Further work

• hoauth2-demo cache enhancement
  Is there way to init all different Apps (AuthCode, ResourceOwnerPassword, ClientCreditials) into one cache?

[freizl]

Hi @ocramz, since you had some experience at using the Experiment module, would you like take a look at this refactor and add any feedback you may have? Thanks in advance.