general security guide - how to secure your QuestDB instance

[pswu11]

We get questions like:

• what do you suggest as best security practices when it comes to deployment?
• what is your current security mechanism i.e. authentication
• how do I add authentication to QuestDB?

We should probably add a guide under "deployment" to cover security topics.

Related Slack conversation: https://questdb.slack.com/archives/C1NFJEER0/p1655360032096149