Che multiuser: Style organization email notifications

[sleshchenko]

It is needed to apply Che style to organization email notifications. Now it is just plain text what is not good UX.

Existing Organization Notifications:

Member added to an Organization

Member Removed from an Organization

Organization Renamed

Organization Removed

[skabashnyuk]

@sleshchenko can you add existed examples so @slemeur can help us with new styles ?

[ghost]

@sleshchenko @skabashnyuk @slemeur should be probably reuse smtht that we use as KeyCloak email templates?

[slemeur]

Yes, we need to be consistent with the styles that we are using in "all" emails that we are sending. Reusing the styles we have defined for keycloak mails should be fine.

[mshaposhnik]

Added styles, but it looks ugly - seems we need more text:
Yahoo:

Gmail:

@slemeur can you provide a wider texts ?

[slemeur]

The texts are the one we used on Codenvy. They are short, but they are going to the point. We can move forward this way.

Ideally, admins from a multi-user Che should be able to modify those emails and style them the way they want (without having to rebuild a new custom Che)

[mshaposhnik]

Done in #6584