Evaluate adapter support for different backends, such as EMQX

[Ayanda-D]

We need to evaluate whether this library can support pooling logic for different backends, such as EMQX, https://www.emqx.io/ (which we can use as an evaluation backend)

[vikger]

Current findings on EMQX usage related to ex_rabbit_pool integration:

Run EMQX in Docker:

docker pull emqx/emqx:v3.1.0
docker run -d --rm --name emqx31 -p 1883:1883 -p 8083:8083 -p 8883:8883 -p 8084:8084 -p 18083:18083 emqx/emqx:v3.1.0

management console: http://localhost:18083 (default user: admin, default password: public)
websocket mode: http://127.0.0.1:18083/#/websocket

elixir plugin available: https://github.com/emqx/emqx-elixir-plugin
uses Erlang dependency: git clone https://github.com/emqtt/emq-relx.git
hooks (used but plugin during load): https://github.com/emqx/emqx
Compile emq-relx with 'make' before using, uncomment emqx-elixir-plugin add/del hooks you need before using.

According to this link, the emq-relx has to be rebuilt with elixir plugin:
https://gh-dark.rauchg.now.sh/emqx/emqx/issues/2645

[vikger]

Using latest image:
docker run -d --rm --name emqx -p 1883:1883 -p 8083:8083 -p 8883:8883 -p 8084:8084 -p 18083:18083 emqx/emqx:latest