Dropdown menu implementation

[nevins321]

• Aidan changed the schema a little bit
• Added a class-management dropdown to the top header of admin pages
• Added support for switching between Universal Admin and individual classes
• Added a Create New Class option to the dropdown
• Connected class creation to the database
• Added separate GET and POST API endpoints for classes
• Automatically redirects users without classes to the class creation page
• Preserves the selected class while navigating between poster/admin pages
• Updated routing for the access hierarchy:Admins can access Universal Admin, poster tools, and reader pages
• Posters can access class-management tools and reader pages
• Readers can access reader pages only
• Faculty & Admin signup now creates a poster account
• Restricted public signup from creating administrator accounts
• Added server-side authorization for class management endpoints

[AidanLoran]

^^Schema change was:

• added missing relationship between poster and user tables (poster now has a required reference to a user)
• removed unused boolean attribute "admin" on user table

[nevins321]

this PR is implementing the class dropdown, class creation, and context navigation. it doesn't include complete class level data isolation. forms, students, progress, raffles, and announcements are still using shared data until class scoped queries, enrollment, and submission validation are implemented, which will be in another pr. i have it pretty much done (its the draft pr called class data isolation) but i need this one reviewed so if there are changes i need to do that before i can finish that one.

[nevins321]

so essentially to be clear our not being able to publish forms and announcements problem isn't fixed till class data isolation pr is done and merged in

[AidanLoran]

putting it here instead of in every file it occurs. Now that we are actually implementing a functional difference between coaches and admins, we really need to use the correct labelling for each (including fixing the deprecated language). This is a separate issue, but it is important.

[AidanLoran]

putting it here instead of in every file it occurs. Now that we are actually implementing a functional difference between coaches and admins, we really need to use the correct labelling for each (including fixing the deprecated language). This is a separate issue, but it is important.

[old] "admin" > "coach", "universal-admin" > "admin"

[nevins321]

yes but thats a later problem

[AidanLoran]

when I first logged in (with admin role && no associated classes), I was directed to "create a class" page and was redirected back each time I tried to navigate out. Good for first time signups, but should not do this to admins. After I created a class, navigation worked as intended

[AidanLoran]

unable to create a class as an admin with no classes

[AidanLoran]

as an admin with no classes, unable to navigate to create class page. I get redirected back to admin homepage