Add role parameter, phase out moderatorPW and attendeePW from create, and password from join

Since version 2.4, BBB can use a parameter that defines the role to be used in the BBB session instead of the so called 'password' with is problematic with modern browsers.

To give a bit of context, the so called `password` used in the URL in plain text is not a real password, but a token or identifier to be used to define the role a user should have in a meeting.

The URLs used by BBB are in some way protected by a hash calculated using a shared secret. Therefore, `password` would not (should not and could not) be used for authenticating the user.

The idea is that

• create would no longer include modPW nor viewerPW,
• join will use instead of password the designated role, such as role=moderator|viewer

See https://github.com/bigbluebutton/bigbluebutton/pull/13589

We will not be removing the password currently, but only adding the role parameter. Phasing out of password use will most likely take place in BBB v2.6