Ensure Cleanup post user / stream deletion

[nitisht]

We need to delete all the stuff a user created or stuff related to a stream when the user or stream is deleted.

For example:

• Dashboards
• Saved filters
• Correlations

[harshithsaiv]

@nitisht Hi, can this issue be assigned to me? Thanks!

[de-sh]

@harshithsaiv feel free to work on the issue, but I believe @hemanth94 is already working on this, you can maybe help him as he goes or look for other issues to contribute to