Concurrency user display

[FalkWolsky]

Proposed changes

If a User A edit an Lowcoder app, and another User B also opens the very same app to edit, both would end up in concurrent overwriting of the app Edit states - as Lowcoder as for now only was made for a single-user as Editor.

In our first attempt to support better multi-user (Editor) experience, we introduce with this PR a optimistic locking strategy. We think it is not a true way to go to try to get a real "multi-user interactivity" for app editing to work. It is not really the case that 2 people same time want collaborative want to edit a single app. Still it can happen that by accident and as rather rare case 2 users open an app independently in the same time.

In this PR we introduce a display for "User B" to get a notice, that a "User A" is editing the app.
After a time window of 3 minutes of inactivity of User A - the lock will be removed and User B can go on to edit the app.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

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