This PR refactors and improves the password hashing code within gitea
and makes it possible for server administrators to set the password
hashing parameters

In addition it takes the opportunity to adjust the settings for `pbkdf2`
in order to make the hashing a little stronger.

The majority of this work was inspired by PR #14751 and I would like to
thank @boppy for their work on this.

Thanks to @gusted for the suggestion to adjust the `pbkdf2` hashing
parameters.

Close #14751

---------

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

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>

* Implement pwn

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Update module

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Apply suggestions mrsdizzie

Co-authored-by: mrsdizzie <info@mrsdizzie.com>

* Add link to HIBP

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add more details to admin command

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Add context to pwn

Signed-off-by: jolheiser <john.olheiser@gmail.com>

* Consistency and making some noise ;)

Signed-off-by: jolheiser <john.olheiser@gmail.com>

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

* Add password requirement info on error

* Move BuildComplexityError to the password pkg

* Unexport complexity type

* Fix extra line

* Update modules/password/password.go

Co-Authored-By: Lauris BH <lauris@nix.lv>

* Fix extra space

* Fix regular expression

* Fix error template name

* Simplify check code, fix default values, add test

* Fix router tests

* Fix fmt

* Fix setting and lint

* Move cleaning up code to test, improve comments

* Tidy up variable declaration

Add password complexity checks. The default settings require a lowercase, uppercase, number and a special character within passwords.

Co-Authored-By: T-M-A <maxim.tkachenko@gmail.com>
Co-Authored-By: Lanre Adelowo <adelowomailbox@gmail.com>
Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>
Co-Authored-By: Lauris BH <lauris@nix.lv>