Fix Permission in API returned repository struct (#25388)

The old code generates `structs.Repository.Permissions` with only
`access.Permission.AccessMode`, however, it should check the units too,
or the value could be incorrect. For example,
`structs.Repository.Permissions.Push` could be false even the doer has
write access to code unit.

Should fix
https://github.com/renovatebot/renovate/issues/14059#issuecomment-1047961128
(Not reported by it, I just found it when I was looking into this bug)

---

Review tips:

The major changes are
- `modules/structs/repo.go`
https://github.com/go-gitea/gitea/pull/25388/files#diff-870406f6857117f8b03611c43fca0ab9ed6d6e76a2d0069a7c1f17e8fa9092f7
- `services/convert/repository.go`
https://github.com/go-gitea/gitea/pull/25388/files#diff-7736f6d2ae894c9edb7729a80ab89aa183b888a26a811a0c1fdebd18726a7101

And other changes are passive.

routers/api/v1/repo/migrate.go

@@ -14,6 +14,7 @@ import (
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/models/organization"
 	"code.gitea.io/gitea/models/perm"
+	access_model "code.gitea.io/gitea/models/perm/access"
 	repo_model "code.gitea.io/gitea/models/repo"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/context"
@@ -211,7 +212,7 @@ func Migrate(ctx *context.APIContext) {
 	}
 
 	log.Trace("Repository migrated: %s/%s", repoOwner.Name, form.RepoName)
-	ctx.JSON(http.StatusCreated, convert.ToRepo(ctx, repo, perm.AccessModeAdmin))
+	ctx.JSON(http.StatusCreated, convert.ToRepo(ctx, repo, access_model.Permission{AccessMode: perm.AccessModeAdmin}))
 }
 
 func handleMigrateError(ctx *context.APIContext, repoOwner *user_model.User, remoteAddr string, err error) {