Add `enable_self_service_portal` variable

[ashishbista]

The variable will give an ability to enable the self service portal, which is disabled by default.

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• [ ] Bugfix (non-breaking change which fixes an issue)
• [x] 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)

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[adenot]

thanks @ashishbista, version 0.4.0 published.