Support github refresh tokens

[anbraten]

closes #3804

Changes

• add expiry when creating user
• rename user.Token to AccessToken
• rename user.Secret to RefreshToken
• add support for github refresh tokens, ignore them if not provided as using an oauth app
• add expiry to gitlab login (prevent direct refresh)

[woodpecker-bot]

Deployment of preview was successful: https://woodpecker-ci-woodpecker-pr-3811.surge.sh

[codecov]

Codecov Report

Attention: Patch coverage is 25.21008% with 89 lines in your changes missing coverage. Please review.

Project coverage is 25.74%. Comparing base (fbb96ff) to head (a656070).
Report is 3 commits behind head on main.

Files	Patch %	Lines
server/forge/github/github.go	5.40%	35 Missing ⚠️
server/forge/gitlab/gitlab.go	21.05%	15 Missing ⚠️
server/forge/forgejo/forgejo.go	42.10%	11 Missing ⚠️
server/forge/gitea/gitea.go	42.10%	11 Missing ⚠️
server/api/login.go	0.00%	7 Missing ⚠️
server/forge/addon/args.go	0.00%	4 Missing ⚠️
...r/forge/bitbucketdatacenter/bitbucketdatacenter.go	33.33%	2 Missing ⚠️
server/forge/bitbucketdatacenter/convert.go	0.00%	2 Missing ⚠️
server/forge/common/utils.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3811      +/-   ##
==========================================
+ Coverage   25.73%   25.74%   +0.01%     
==========================================
  Files         366      366              
  Lines       27034    27008      -26     
==========================================
- Hits         6956     6954       -2     
+ Misses      19538    19514      -24     
  Partials      540      540              

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