[WIP] feat: Build Student Onboarding Workflow

[NewtonLC]

Checklist:

• I have read freeCodeCamp's contribution guidelines.
• My pull request has a descriptive title (not a vague title like Update index.md)

Closes #596

Fixed Join Page and added instructions for enabling permission on FreeCodeCamp Proper TODO: Implement 'Connect' button functionality. This requires Mrugesh's PR #66063 to be implemented. Currently, the Connect button just adds the user to the Classroom without verification.

Description

Here's a description of the Student Invitation / Onboarding from Start to Finish:

1. A teacher obtains the invite code for their class by clicking the "Invite" button in the dropdown for their class.
2. The teacher shares this invite link with their students. This can be done through a group email, sharing the link via Peardeck, Canvas, Google Classroom, etc.
3. The students click on the join link, which takes them to FCC Classroom.
4. The students are not logged in at this point, so Classroom prompts them to log in.
5. Upon sign in, the students see a Join Page prompting them to connect to their teacher's classroom, along with instructions to enable Classroom Access on FCC Proper before connecting to the classroom.
6. The students are taken to their settings page in FCC Proper.
   6a. If a student does not have an FCC Proper account, FCC Proper will ask them to sign in first.
7. The students return to the Join Page and click the "Connect" button.

What's Blocking this PR from fully working?

• PR #66063 needs to be merged in, as it implements the FCC Classroom permission feature as well as the get-user-id endpoint, which is required for the "Connect" feature to work.