Support creating database instance with encryption enabled

[botanical]

This is a request to modify the airflow_db resource definition so that we can set storage_encrypted to true
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/db_instance

This request is coming from a security ask that ensures we have our RDS DB instances encrypted at rest enabled https://github.com/NASA-IMPACT/veda-architecture/issues/623

[aliziel]

@amarouane-ABDELHAK Could I be added to the repo as a writer or maintainer ? (or triage, if you don't mind me bothering you for higher privilege actions -- everyone else is on PTO !)

[amarouane-ABDELHAK]

Done

[aliziel]

Released in v1.1.13 after successful preprod encryption in CSDA + VEDA.

1. Expose storage_encrypted on database submodule
   1. NASA-IMPACT consumers will likely need this to be true if deploying in MCP
   2. Currently set as a required input
2. Allow deletion_protection configurability on database resource to enable restoration from snapshot for existing instances
   1. Operation performs implicit delete + recreate, which deletion_protection (correctly) prevents
   2. Default to true to otherwise retain layer of protection

NOTE: I considered a followup on 1.ii to make the storage_encrypted setting optional, but we reached a consensus to leave it required (thread). Main points:

Considerations - Known instances have fewer CI safeguards (e.g. tf plan, TF_INPUT=0)
Advantages - Greater chance of saving future instances from time-expensive exercise
Mitigating Factors - Coordination with other instances, followup CI enhancements (#32, NASA-IMPACT/veda-data-airflow#334)