Update achievements to work with notification object

[phillipthelen]

The way achievements are displayed on web is often done by comparing the fields directly. Instead the server should update the notifictations property on the user to add information about the gained notification. Same way it is already done for the Ultimate Gear achievements or Back to basics. This is essential for the achievements to work properly across the mobile apps and the website.

List of achievements that need to be updated:

• Beast Master/Mount Master/Triad Bingo
• Party Up
• Party On
• Mind over matter
• Lost Masterclasser
• just add water

I marked this as Help Wanted in case a contributor wants to work on one or multiple of these before I have time.

[Xaz16]

Hello @phillipthelen! Is it still Help wanted issue? As I can see we already have PR for that

[paglias]

@Xaz16 I'll remove the label as this is being handled by @phillipthelen

[Xaz16]

@paglias thank you :)

[beffymaroo]

@SabreCat Should this one get a Help Wanted tag again?

[SabreCat]

oh gosh, absolutely. Not touched since 2019!

[CuriousMagpie]

I'll take this one, too, since I'm also handling #11541 and they're related.