the module doesn't permit to do read replicate

This kind of resource should be enough to do an RDS read replicate ...

resource "aws_db_instance" "db_replica_main_postgresql" {
  instance_class              = "db.${var.rds_main_postgres_instance_type}"
  skip_final_snapshot         = true
  backup_retention_period     = 7
  replicate_source_db         = module.db_main_postgres.db_identifier
}

But the module demands a "freetext" to create a "db_name" and an "engine_version" ...
They shouldn't be required when "replicate_source_db" is given

Without "freetext" :

╷
│ Error: Missing required argument
│ 
│   on rds-main-postgres.tf line 88, in module "db_replica_main_postgresql":
│   88: module "db_replica_main_postgresql" {
│ 
│ The argument "freetext" is required, but no definition was found.
╵

Without "engine_version"

╷
│ Error: Missing required argument
│ 
│   on rds-main-postgres.tf line 88, in module "db_replica_main_postgresql":
│   88: module "db_replica_main_postgresql" {
│ 
│ The argument "engine_version" is required, but no definition was found.
╵

With "freetext" and "engine_version"

╷
│ Error: Conflicting configuration arguments
│ 
│   with module.db_replica_main_postgresql[1].aws_db_instance.postgresql_instance,
│   on .terraform/modules/db_replica_main_postgresql/main.tf line 39, in resource "aws_db_instance" "postgresql_instance":
│   39:   db_name  = replace("dbiaas-${local.identifier}", "-", "")
│ 
│ "db_name": conflicts with replicate_source_db
╵