Added compatibility for Grails 3.3 together with Multi-Tenancy.

[jhron]

Data sources are now taken from existing beans directly instead of configuration files. So it works with dynamically created data sources too and not only with data sources defined in configuration files.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

✅ jhron
✅ ivo-k
❌ Puneet Behl

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[puneetbehl]

Please rebase, resolve the conflicts, and sign the CLA.