docs: document eduPUSH type and deprecate Push Token Type

[Luc1412]

This pull request updates documentation regarding:

• EduPush Token Type
• Mark old push token type as legacy and provides deprecation note

[Luc1412]

@fritterhoff How do we want to communicate the change?

• Do we want to call our new edupush token type Push Token or do we want to refer EduPush Token or eduPush Token or Edupush Token.
• Depending on the first decision, how do we want to refer to the old Push Token type? Legacy Push Token or simply Push Token
• If there are mentions of Push Token types, how do we want to refer to them? Should we mention both, just Edupush or should we summarize them as Push Token types?

Here also some special cases that needs to be clarified:

SMS Gateway Config

There it mentions the setup of firebase. The old docs refer to SLA with NetKnights to use the privacyIDEA app.

Now it's managed by GWDG, but how do people get access to our Firebase instance?

WebUI Config

There are show_android_privacyidea_authenticator and show_ios_privacyidea_authenticator we didn't replaced yet. What happens to these options?

Supported Tokens - Apps

There it mentions privacyIDEA Authenticator for HOTP, TOTP and PUSH. Should we keep it or remove it?

[fritterhoff]

• I would suggest eduMFA Push Token
• We should use Legacy Push Token
• Right now I would summarize them

Right now I check with the GWDG whats the preferred way to get access.

I think we should replace/extend the existing options... Maybe in the same PR or in a new.

Regarding HTOP, TOTP -> #288

[fritterhoff]

The preferred way is to write an email to support@gwdg.de