[#58] Mattermost Device support

.env.mattermost

docker-compose.full.yml

docker-compose.local.yml

docker-compose.test.yml

docker-compose.yml

docker/activemq/conf/activemq.xml

docker/activemq/mattermost_consumer.conf

docker/activemq/mattermost_dlq_consumer.conf

docker/activemq/mattermost_publisher.conf

notifications_consumer/config.py

notifications_consumer/processors/__init__.py

notifications_consumer/processors/mattermost/processor.py

notifications_consumer/processors/mattermost/utils.py

poetry.lock

pyproject.toml

scripts/docker-send-mattermost.py