refactor!: integrate feedback on alpha release

[rflechtner]

fixes KILTProtocol/ticket#3540

• breaking: unnest selective disclosure parameters dc8d458
• breaking: fully switch to using named parameters on credentials functions 3c17ace
• non-breaking: allow passing key pairs & signers as submitter parameter on issue() bcd882f

How to test:

• Actually trying the new interfaces could be done on the beta that is to be released
• Tests for new features are yet to be written

Checklist:

• I have verified that the code works
• I have verified that the code is easy to understand
  • If not, I have left a well-balanced amount of inline comments
• I have left the code in a better state
• I have documented the changes (where applicable)
  • Either PR or Ticket to update the Docs
  • Link the PR/Ticket here

[rflechtner]

@abdulmth I'm not sure about the nesting of parameters, seems cumbersome and messy to me. How did you see it? Should we flatten parameters a bit more?

I would keep the issuer and holder objects but maybe flatten the various options objects.

[Dudleyneedham]

LGTM. It feels more consistent

[Dudleyneedham]

@abdulmth I'm not sure about the nesting of parameters, seems cumbersome and messy to me. How did you see it? Should we flatten parameters a bit more?

I would argue to call them all options, that would move them up one level.

I would keep the issuer and holder objects but maybe flatten the various options objects.

Yes, I would agree.

[rflechtner]

@abdulmth had argued that the proof/presentationOptions to carry semantic value. We did decide to group options this way at some point and I'm not sure we want to change that last minute without good reason, so I'd just leave it.