Limit to one mscolab window per mss

[Shivashis Padhi]

Currently, one can open any number of mscolab window on one instant of mss. As discussed on slack group, it should be limited to one until other issues with mscolab are fixed.

[Shivashis Padhi]

assigning this issue to @Sakshi Chopkar

[Sakshi Chopkar]

@shiv Thank you!

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[Tanish Grover]

@Sakshi Chopkar are you working on this issue?

[Sakshi Chopkar]

Yes

[Reimar Bauer]

please run pytest before a PR

[Reimar Bauer]

see #504

[Reimar Bauer]

Allowed only one mscolab instance, fixes issue #504 and issue #506

→ <<cset 06cfb1175b84>>

[Reimar Bauer]

Merged in tanish19/mss/single_mscolab_instance (pull request #822)

Allowed only one mscolab instance, fixes issue #504 and issue #506

→ <<cset 6e329a740784>>