In investigating #7947 it has become clear that the storage component of go-git repositories needs closing.
This PR adds this Close function and adds the Close functions as necessary.
In TransferOwnership the ctx.Repo.GitRepo is closed if it is open to help prevent the risk of multiple open files.
Fixes#7947
* Send email to assigned user
* Only send mail if enabled
* Mail also when assigned through API
* Need to refactor functions from models to issue service
* Refer to issue index rather than ID
* Disable email notifications completly at initalization if global disable
* Check of user enbled mail shall be in mail notification function only
* Initialize notifications from routers init function.
* Use the assigned comment when sending assigned mail
* Refactor so that assignees always added as separate step when new issue/pr.
* Check error from AddAssignees
* Check if user can be assiged to issue or pull request
* Missing return
* Refactor of CanBeAssigned check.
CanBeAssigned shall have same check as UI.
* Clarify function names (toggle rather than update/change), and clean up.
* Fix review comments.
* Flash error if assignees was not added when creating issue/pr
* Generate error if assignee users doesn't exist
* extract actions on new pull request from models to pulls service
* improve code
* move code.gitea.io/gitea/modules/pull to code.gitea.io/gitea/services/pull
* fix fmt
* Rename pulls.go to pull.go
