Change all license headers to comply with REUSE specification.

Fix #16132

Co-authored-by: flynnnnnnnnnn <flynnnnnnnnnn@github>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>

* Move some files into models' sub packages

* Move functions

* merge main branch

* Fix check

* fix check

* Fix some tests

* Fix lint

* Fix lint

* Revert lint changes

* Fix error comments

* Fix lint

Co-authored-by: 6543 <6543@obermui.de>

* Use a struct as test options

* Fix name

* Fix test

* Move user functions into user.go

* Fix test

* Move UserRedirect into models/user/

* Fix lint & test

* Fix lint

* Fix lint

* remove nolint comment

* Fix lint

* Move user follow and openid into models/user

* Ignore the lint

* Ignore the lint

* Fix test

* ignore stutters lint on UserOpenID

* Move EmailAddress into models/user/

* Fix test

* rename user_mail to user_email

* Fix test

* Move UserRedirect into models/user/

* Fix lint & test

* Fix lint

* Fix lint

* remove nolint comment

* Fix lint

* issue content history

* Use timeutil.TimeStampNow() for content history time instead of issue/comment.UpdatedUnix (which are not updated in time)

* i18n for frontend

* refactor

* clean up

* fix refactor

* re-format

* temp refactor

* follow db refactor

* rename IssueContentHistory to ContentHistory, remove empty model tags

* fix html

* use avatar refactor to generate avatar url

* add unit test, keep at most 20 history revisions.

* re-format

* syntax nit

* Add issue content history table

* Update models/migrations/v197.go

Co-authored-by: 6543 <6543@obermui.de>

* fix merge

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lauris BH <lauris@nix.lv>

* Move db related basic functions to models/db

* Fix lint

* Fix lint

* Fix test

* Fix lint

* Fix lint

* revert unnecessary change

* Fix test

* Fix wrong replace string

* Use *Context

* Correct committer spelling and fix wrong replaced words

Co-authored-by: zeripath <art27@cantab.net>

* Move pull request api convert to convert package

* Rename ToPullRequest to ToAPIPullRequest

* Fix counts on issues dashboard

* setupSess -> setupSession

* Unit test

* Load repo owners for issues