Closes#1789.
The bug was due to the fact that GitLab does not guarantee that issue numbers are created sequentially: some identifiers can be skipped. Therefore, the new pull requests numbers should not be offset by the number of issues, but by the maximum issue number.
See for instance https://gitlab.com/troyengel/archbuild/-/issues/?sort=created_date&state=all&first_page_size=20, where there is only a singe issue with number "2".
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/1790
Co-authored-by: Antonin Delpeuch <antonin@delpeuch.eu>
Co-committed-by: Antonin Delpeuch <antonin@delpeuch.eu>
(cherry picked from commit 2c185c39fe600041701d5f59cb1076a788815cb4)
(cherry picked from commit 8f68dc4c9c2f0acab55d59a496b0f141befad969)
(cherry picked from commit 7e932b7fca1b119e7cc646183c383ba51a5f1d14)
(cherry picked from commit 6bbe75ecf8ac502bd42ff5765e6e7733f290a54e)
(cherry picked from commit b18c2e8d658c3311e0a299696bd1b6612c52ef13)
Conflicts:
services/migrations/gitlab.go
https://codeberg.org/forgejo/forgejo/pulls/2075
(cherry picked from commit abc129c762b3c1a992ad5c67adf62d8336eadbbe)
(cherry picked from commit 28884fac10c455a9f40bebd961fca40afd4a749e)
(cherry picked from commit 5f528dd85fa6705c60d15bce616a46f00df1b85b)
(cherry picked from commit cb9b8a31b25b27fa5e386b20f02e532bbf3462a2)
(cherry picked from commit 97f02df163e2b4e23b82e23e5ef57a586b17f021)
(cherry picked from commit 4611e10e6acef9185e1f8c84e63d1fe95fcf6436)
