docs: add more warnings for default secrets and docker-compose

[dpgaspar]

SUMMARY

Add more warnings on our default for docker-compose and stress out the importance of having a unique random SECRET_KEY

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[sfirke]

@dpgaspar I left a suggestion to change from quote format to caution format (you can see an example of how that renders on the docker compose install page). And I put a note in there about keeping your key, what do you think about that? People have written in Slack about getting locked out of their Superset instance when they don't know their SECRET_KEY that they randomly generated. Maybe they store it as an env variable and then delete a file or wipe out a VM or something.

[sfirke]

Suggested change

	Make sure you are changing this key for your deployment with a strong key.
	Ensure your deployment uses a strong, unique key.
	Store this key securely. Without this key, you will be unable to access your Superset metadata database. That is, you will lose all of your Superset dashboards, charts, etc. :::

[csummers]

This :::caution block as merged is not closed with a :::, so this page renders everything after like so:

The suggestion did have a closing :::, though.

[sfirke]

Thanks @csummers! I have a PR open now to fix this.

[mistercrunch]

One thing I was thinking about recently around ENVIRONMENT_TAG_CONFIG and SUPERSET_ENV is we could either force a very visible tag or refuse to start when use a bad combination of things (default SECRET_KEY and "SUPERSET_ENV=production").

Also was thinking that in-your-face, "things you should know" in dev would be useful, notices like "hey we noticed you're on python 3.9 - the supported version is now 3.10, you should upgrade"