allow to use different db engine type (outerbounds#35)

Author: oavdeev

modules/datastore/README.md

@@ -19,7 +19,7 @@ To read more, see [the Metaflow docs](https://docs.metaflow.org/metaflow-on-aws/
 
 | Name | Description | Type | Default | Required |
 |------|-------------|------|---------|:--------:|
-| <a name="input_db_engine"></a> [db\_engine](#input\_db\_engine) | n/a | `string` | `"postgresql"` | no |
+| <a name="input_db_engine"></a> [db\_engine](#input\_db\_engine) | n/a | `string` | `"postgres"` | no |
 | <a name="input_db_engine_version"></a> [db\_engine\_version](#input\_db\_engine\_version) | n/a | `string` | `"11"` | no |
 | <a name="input_db_instance_type"></a> [db\_instance\_type](#input\_db\_instance\_type) | RDS instance type to launch for PostgresQL database. | `string` | `"db.t2.small"` | no |
 | <a name="input_db_name"></a> [db\_name](#input\_db\_name) | Name of PostgresQL database for Metaflow service. | `string` | `"metaflow"` | no |

modules/datastore/variables.tf

@@ -6,7 +6,7 @@ variable "db_instance_type" {
 
 variable "db_engine" {
   type    = string
-  default = "postgresql"
+  default = "postgres"
 }
 
 variable "db_engine_version" {