Refactored and fixed migration tests

[KN4CK3R]

I've refactored and fixed the migration tests. They now use all the same test methods.
The tests for Gitlab, Gitea and Gogs were broken and are fixed now.
I removed the usage of time.Now() in the downloaders because you can't write normal tests with changing values. Empty timestamps are now populated in the uploader.

Other changes/fixes:

• GiteaLocalUploader
  • Set Milestone.CreatedUnix/UpdatedUnix
• GitlabDownloader
  • Use MergeRequestApprovals.GetConfiguration instead of MergeRequestApprovals.GetApprovalState
• GogsDownloader
  • Set Issue.PosterID and Issue.Updated

[codecov-commenter]

Codecov Report

Merging #16714 (a4f3690) into main (ea07726) will decrease coverage by 0.01%.
The diff coverage is 18.58%.

@@            Coverage Diff             @@
##             main   #16714      +/-   ##
==========================================
- Coverage   45.38%   45.37%   -0.02%     
==========================================
  Files         758      758              
  Lines       85306    85381      +75     
==========================================
+ Hits        38713    38738      +25     
- Misses      40313    40362      +49     
- Partials     6280     6281       +1     

Impacted Files	Coverage Δ
modules/migrations/gitea_downloader.go	0.93% <0.00%> (ø)
modules/migrations/gitea_uploader.go	6.77% <0.00%> (-0.63%)	⬇️
modules/migrations/gitlab.go	0.99% <0.00%> (+<0.01%)	⬆️
modules/migrations/gogs.go	2.36% <0.00%> (+0.01%)	⬆️
models/models.go	52.88% <33.33%> (-0.54%)	⬇️
models/token.go	69.04% <77.27%> (+2.38%)	⬆️
modules/setting/setting.go	49.90% <100.00%> (+0.09%)	⬆️
services/auth/source/oauth2/providers_custom.go	63.23% <100.00%> (ø)
services/pull/pull.go	41.78% <0.00%> (ø)
models/gpg_key_common.go	64.51% <0.00%> (+4.83%)	⬆️
... and 1 more

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[zeripath]

Could you update the initial comment to explain that you've fixed some other little bugs too?

I see for example you've set the PosterID in Gogs which was previously missing.

[KN4CK3R]

Could you update the initial comment to explain that you've fixed some other little bugs too?

I see for example you've set the PosterID in Gogs which was previously missing.

done