Allow to enable/disable multi_az option on master node and remove read_replica_2 instance on dev*

[owl-king]

Support:

• multi_az on RDS master node
• read_replica_2 instance

With enable_rds_main_multiaz = true and create_read_replica_2 = true (default values that works for mainnet, testnet ), this requires changes in state due to index. No new resources are created or deleted. Plan is below

  # aws_db_instance.read_replica_2 has moved to aws_db_instance.read_replica_2[0]
    resource "aws_db_instance" "read_replica_2" {
        id                                    = "dev*-indexer-apne1-db-read-replica-2"
        name                                  = "dydx"
        tags                                  = {
            "Environment" = "dev*"
            "Name"        = "dev*-indexer-apne1-db-read-replica-2"
        }
        # (52 unchanged attributes hidden)
    }

  # aws_route53_record.read_replica_2 has moved to aws_route53_record.read_replica_2[0]
    resource "aws_route53_record" "read_replica_2" {
        id                               = "***"
        name                             = "postgres-main-rr.dydx-indexer.private"
        # (7 unchanged attributes hidden)

        # (1 unchanged block hidden)
    }

With enable_rds_main_multiaz = false and create_read_replica_2 = false, this will delete read_replica_2 instance + route53 records and changes multi_az option. Plan is below

~ resource "aws_db_instance" "main" {
        id                                    = "dev*-indexer-apne1-db"
      ~ multi_az                              = true -> false
        name                                  = "dydx"
        tags                                  = {
            "Environment" = "dev*"
            "Name"        = "dev*-indexer-apne1-db"
        }
        # (63 unchanged attributes hidden)
    }

  # aws_db_instance.read_replica_2[0] will be destroyed
  # (because index [0] is out of range for count)
  # (moved from aws_db_instance.read_replica_2)
  - resource "aws_db_instance" "read_replica_2" {
   .......
   }

[ttl33]

would there be a case where the values of these will be different? for example,

create_read_replica_2 = true, enable_rds_main_multiaz = false?

if these two values will stay the same, then would it make sense to combine them into a single variable?

[owl-king]

Yes. It could be possible to be different. For example, if on dev, you want to test the load distribution between read replicas then you should let create_read_replica_2 = true. enable_rds_main_multiaz should be false on dev because that's wasted

[owl-king]

Close the PR as the workflow changes to optimize-aws-cost branch