NOISSUE - Add DTLS support to CoAP messaging

[felixgateru]

What does this do?

Add DTLS support to CoAP messaging

Which issue(s) does this PR fix/relate to?

None

List any changes that modify/break current functionality

Refactor: Updated the nginx reverse proxy with CoAP stream. Refactor: Add internal server configuration for DTLS support.

Have you included tests for your changes?

No

Did you document any new/modified functionality?

No

Notes

To be merged after https://github.com/mainflux/mainflux/pull/1918

[arvindh123]

LGTM

In Future it will nice if coap server have CID support https://www.linkedin.com/pulse/what-dtls-connection-id-mieszko-mieru%C5%84ski/

Reference code for ID https://github.dev/plgd-dev/go-coap/blob/master/examples/dtls/cid/server/main.go