Migrate from mattermost docker compose to mattermost kubernetes operator

Troubleshooting
9

The mattermost operator runs an init container that checks for DB connection before it starts the mattermost container.

If the postgres connection was not happening, the init container would fail. But for me, it did not fail.

See code: https://github.com/mattermost/mattermost-operator/blob/0202e3e5a6c5960fe277fd8e24441b6743780168/pkg/mattermost/database_external.go#L105-L116