limiting access to buffers to workspace users

[alemidev]

buffers should be divided per workspace, preventing attaching to just any buffer

• when connecting to a buffer, some form of validation must be provided
• connecting to foreign buffers should be impossible and must not be permitted

[alemidev]

more notes on this for clarity: while the server will reject these connections because of non-matching auth, clients still must make it impossible for their users to do "something wrong", in this case trying to attach to buffers before joining a workspace.

Practical example: on nvim there's a :MP attach command, which attaches a buffer. This command is unavailable as long as user isn't in any workspace!