feat: add CanSetUserinfoFromRequest interface

[muir]

To support adding session-related claims (like a session id) to IDTokens, I've added a new (optional) add-on interface to Storage:

// CanSetUserinfoFromRequest is an optional additional interface that may be implemented by
// implementors of Storage.  It allows additional data to be set in id_tokens based on the
// request.
type CanSetUserinfoFromRequest interface {
	SetUserinfoFromRequest(ctx context.Context, userinfo oidc.UserInfoSetter, request IDTokenRequest, scopes []string) error
}

For the next branch, we can simply add request IDTokenRequest as an additional parameter to SetUserinfoFromScopes

[codecov]

Codecov Report

Merging #322 (e56925a) into main (eea2ed1) will increase coverage by 0.02%.
The diff coverage is 57.14%.

@@            Coverage Diff             @@
##             main     #322      +/-   ##
==========================================
+ Coverage   39.63%   39.65%   +0.02%     
==========================================
  Files          74       74              
  Lines        5965     5972       +7     
==========================================
+ Hits         2364     2368       +4     
- Misses       3350     3352       +2     
- Partials      251      252       +1     

Impacted Files	Coverage Δ
pkg/op/token.go	64.10% <40.00%> (-1.08%)	⬇️
example/server/storage/storage.go	60.86% <100.00%> (+0.20%)	⬆️

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