Feat/support authentication plugins like ldap simple

[alereca]

Description of your changes

Fixes #125

I have:

• [x] Read and followed Crossplane's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.

How has this code been tested

Added unit test for user controller create and update methods

• UserWithAnAuthPluginThatNotRequiresPassword (for both)

[Duologic]

Would you mind rebasing?

[mcanevet]

@alereca are you still interested in this feature? I'd like to see this merged, I can rebase and open a new PR crediting your work if you want.

[alereca]

@alereca are you still interested in this feature? I'd like to see this merged, I can rebase and open a new PR crediting your work if you want.

@mcanevet I would greatly appreciate it. Currently, I'm quite busy working on some quarterly job tasks and finishing my studies. Please let me know if you have any questions about anything here.

[alereca]

Would you mind rebasing?

@Duologic Sorry I didn't answer before

[mcanevet]

@alereca I think I underestimated the complexity of the conflicts. I'm not sure how to fix the one on reconciler.go: https://gist.github.com/mcanevet/24b2fde49eab35c4ed717a4ebb5badf2