misc: Allow setting init_containers with null condition

This change allows configuring `init_containers` that are not added to
the `depends_on` list for the main container, by setting `null` as the
container `condition`.

This is useful for containers that actually depend on the main
container, and not the other way around. For example, a `nginx` sidecar
that needs to wait for the main container to be healthy before starting.

By allowing `null` as the container condition, this is a non-breaking
change.

README.md

@@ -297,7 +297,7 @@ Available targets:
 | <a name="input_id_length_limit"></a> [id\_length\_limit](#input\_id\_length\_limit) | Limit `id` to this many characters (minimum 6).<br/>Set to `0` for unlimited length.<br/>Set to `null` for keep the existing setting, which defaults to `0`.<br/>Does not affect `id_full`. | `number` | `null` | no |
 | <a name="input_ignore_changes_desired_count"></a> [ignore\_changes\_desired\_count](#input\_ignore\_changes\_desired\_count) | Whether to ignore changes for desired count in the ECS service | `bool` | `false` | no |
 | <a name="input_ignore_changes_task_definition"></a> [ignore\_changes\_task\_definition](#input\_ignore\_changes\_task\_definition) | Ignore changes (like environment variables) to the ECS task definition | `bool` | `true` | no |
-| <a name="input_init_containers"></a> [init\_containers](#input\_init\_containers) | A list of additional init containers to start. The map contains the container\_definition (JSON) and the main container's dependency condition (string) on the init container. The latter can be one of START, COMPLETE, SUCCESS or HEALTHY. | <pre>list(object({<br/>    container_definition = any<br/>    condition            = string<br/>  }))</pre> | `[]` | no |
+| <a name="input_init_containers"></a> [init\_containers](#input\_init\_containers) | A list of additional init containers to start. The map contains the container\_definition (JSON) and the main container's dependency condition (string) on the init container. The latter can be one of START, COMPLETE, SUCCESS, HEALTHY, or null. If null, the init container will not be added to the depends\_on list of the main container. | <pre>list(object({<br/>    container_definition = any<br/>    condition            = string<br/>  }))</pre> | `[]` | no |
 | <a name="input_label_key_case"></a> [label\_key\_case](#input\_label\_key\_case) | Controls the letter case of the `tags` keys (label names) for tags generated by this module.<br/>Does not affect keys of tags passed in via the `tags` input.<br/>Possible values: `lower`, `title`, `upper`.<br/>Default value: `title`. | `string` | `null` | no |
 | <a name="input_label_order"></a> [label\_order](#input\_label\_order) | The order in which the labels (ID elements) appear in the `id`.<br/>Defaults to ["namespace", "environment", "stage", "name", "attributes"].<br/>You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present. | `list(string)` | `null` | no |
 | <a name="input_label_value_case"></a> [label\_value\_case](#input\_label\_value\_case) | Controls the letter case of ID elements (labels) as included in `id`,<br/>set as tag values, and output by this module individually.<br/>Does not affect values of tags passed in via the `tags` input.<br/>Possible values: `lower`, `title`, `upper` and `none` (no transformation).<br/>Set this to `title` and set `delimiter` to `""` to yield Pascal Case IDs.<br/>Default value: `lower`. | `string` | `null` | no |