[BUG] WorkspaceInvitation model stores workspace_name string instead of workspace_id foreign key; accept_invitation endpoint never implemented

[vipul674]

Description of the Bug

The workspace invitation system has two related bugs that make it non-functional:

Bug 1: WorkspaceInvitation model uses workspace_name instead of workspace_id

In backend/app/models.py, the WorkspaceInvitation model stores workspace_name: str rather than a workspace_id foreign key. When an invitation is accepted, there is no way to reliably look up the actual workspace because:

• The workspace could have been renamed since the invitation was created
• The workspace could have been deleted
• Multiple workspaces could share the same name
• There is no database constraint enforcing referential integrity

Bug 2: accept_invitation endpoint does not exist

Looking at backend/app/routes/workspaces.py and the FastAPI router includes in main.py, there is no accept_invitation endpoint. Even if invitations could be sent (see Bug #736), there is no way for the invited user to accept them. The invitation feature is half-implemented - it supports creating invitations but not consuming them.

Steps to Reproduce

1. As a user, receive a workspace invitation link (however it's delivered)
2. There is no API endpoint to accept the invitation
3. The invitation feature is non-functional end-to-end

Expected Behavior

1. WorkspaceInvitation model should have a workspace_id foreign key pointing to the Workspace table
2. There must be a POST /api/v1/workspaces/invitations/{invitation_id}/accept endpoint
3. Accepting an invitation should add the user as a member of the workspace

Affected Files

• backend/app/models.py (WorkspaceInvitation model)
• backend/app/routes/workspaces.py (missing accept_invitation endpoint)

Suggested Fix

1. Add workspace_id: Mapped[str] = mapped_column(ForeignKey("workspaces.id")) to WorkspaceInvitation
2. Implement an acceptance endpoint that validates the invitation token, finds the workspace, creates a WorkspaceMember record, and marks the invitation as accepted

GSSoC '26

• Yes, I am participating in GirlScript Summer of Code and would like to fix this.

[github-actions]

Hi @vipul674! 👋

Thanks for opening this issue! We are thrilled to have you contribute to PDF-Assistant-RAG for GSSoC 2026.

📌 Before you start:

• Make sure you have read our Contributing Guidelines.
• Wait for a project admin to assign this issue to you before working on it.
• Remember to branch off dev and not main.

Happy Coding! 🚀

[vipul674]

@param20h I would like to work on this issue under GSSoC 2026. Please assign it to me.