Added more info on security, RDS, and ALLOWED_HOST configs

[ekansa]

brief description of changes

Updates AWS deployment documentation to discuss networking and security groups.

issues addressed

Provides additional information about how to use security groups to grant the minimal needed permissions between different nodes in a distributed architecture. Also discusses some useful settings.

further comments

We may want to add more information about connecting to RDS instances in future updates

---

This box must be checked

• [X] the PR branch was originally made from the base branch

This box should be checked

• [X] after these changes the docs build locally without error

This box should only be checked you intend to follow through on it (we can do it on our end too)

• [ ] I will cherry-pick all commits in this PR into other branches that should have them after this PR is merged

[ekansa]

Self approving this update. Thanks to @aarongundel for walking me through an AWS deployment (but if I muddled anything, it's my fault, not his).