Simplify login form view customization

[adamwojs]

Question	Answer
Tickets	-
Bug fix?	no
New feature?	yes
BC breaks?	no
Tests pass?	yes
Doc needed?	yes
License	GPL-2.0

In order to simplify login form template (src/bundle/Resources/views/themes/admin/account/login/index.html.twig) customization:

• Restructured template using blocks
• Added login-form-before and login-form-after components groups

Example use case

Assuming that as a Developer I would like to would like to add "Login via XYZ" button to login form. 

1. Create  /templates/login_via_oauth2.html.twig

<div class="row mt-4">
    <div class="col">
        <p class="text-center">or</p>

        <div class="btn-group d-flex">
            <a href="#" class="btn btn-primary mr-1">
                Login via Google
            </a>

            <a href="#" class="btn btn-primary ml-1">
                Login via  Microsoft
            </a>
        </div>
    </div>
</div>

2. Add component definition to /config/services.yaml:

    app.components.login_via_aouth2:
        parent: EzSystems\EzPlatformAdminUi\Component\TwigComponent
        arguments:
            $template: 'login_via_oauth2.html.twig'
        tags:
            - { name: ezplatform.admin_ui.component, group: login-form-after }

3. Done. 

Checklist:

• Coding standards ($ composer fix-cs)
• Ready for Code Review

[bogusez]

@adamwojs is this new buttons are just mockups? I'm asking because when I'm clicking on them nothing happens (no errors in console etc).

[adamwojs]

This PR is only about introducing new extension points to login form view. Login will not gonna work without ibexa/oauth2-client and few other steps 🙃

[bogusez]

This PR is only about introducing new extension points to login form view. Login will not gonna work without ibexa/oauth2-client and few other steps 🙃

OK thank you :)

[lserwatka]

Let's not waste time on this one and merge it as it is.

[bogusez]

Let's not waste time on this one and merge it as it is.

It's ready to be merge

[lserwatka]

We need to document this example

[lserwatka]

@ezsystems/documentation-team