fix: postgresqlflex flavor errors (#107)

feat: enable old v2 flavor handling
Co-authored-by: Marcel S. Henselin <marcel.henselin@stackit.cloud>
Reviewed-on: #107

docs/data-sources/postgresflexalpha_instance.md

@@ -42,10 +42,16 @@ data "stackitprivatepreview_postgresflexalpha_instance" "example" {
 - `flavor_id` (String) The id of the instance flavor.
 - `id` (String) internal ID
 - `is_deletable` (Boolean) Whether the instance can be deleted or not.
+- `labels` (Map of String) Key-value pairs, 63 characters max, begin and end with an alphanumerical character,
+may contain dashes (-), underscores (_), dots (.), and alphanumerics between. Key MUST be at least 1 character.
+Max 64 labels
+Regex for keys: ^(?=.{1,63}$)([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]$
+Regex for values: ^(?=.{0,63}$)(([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9])*$
+The stackit- prefix is reserved and cannot be used for Keys.
 - `name` (String) The name of the instance.
 - `network` (Attributes) The access configuration of the instance (see [below for nested schema](#nestedatt--network))
 - `replicas` (Number) How many replicas the instance should have.
-- `retention_days` (Number) How long backups are retained. The value can only be between 32 and 365 days.
+- `retention_days` (Number) How long backups are retained. The value can only be between 32 and 90 days.
 - `status` (String) The current status of the instance.
 - `storage` (Attributes) The object containing information about the storage size and class. (see [below for nested schema](#nestedatt--storage))
 - `tf_original_api_id` (String) The ID of the instance.