added mongodb support

[arafato]

Hi --,

this is a very initial version without unit tests. Since this is often demanded from customers I wanted to check and review the current state with you if you think it makes sense to work on this. Thanks!

[xiaozhu36]

HI @arafato Thanks for your contribution. At present, this repo has been deprecated and can you move the pr into https://github.com/terraform-providers/terraform-provider-alicloud?

[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 7 committers have signed the CLA.

✅ xiaozhu36
✅ arafato
❌ tf-release-bot
❌ wzb56
❌ dianmuali
❌ tombuildsstuff
❌ geeklenny

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