blueprints: OCI registry support (#3500)

* blueprints: add ability to load blueprints via OCI

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* add docs

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* fix inheritance check for meta models

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* add oci tests

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

website/developer-docs/blueprints/v1/meta.md

@@ -0,0 +1,23 @@
+# Meta models
+
+Since blueprints have a pretty strict mapping of each entry mapping to an instance of a model in the database, _meta models_ have been added to trigger other actions within authentik that don't directly map to a model.
+
+### `authentik_blueprints.metaapplyblueprint`
+
+This meta model can be used to apply another blueprint instance within a blueprint instance. This allows for dependency management and ensuring related objects are created.
+
+#### Attributes
+
+-   `identifiers`: Key-value attributes used to match the blueprint instance
+
+    Example:
+
+    ```yaml
+    attrs:
+        identifiers:
+            name: Default - Password change flow
+    ```
+
+-   `required`: (Default: `true`) Configure if the blueprint instance must exist
+
+    If this is set to `true` and no blueprint instance matches the query above, an error will be thrown. Otherwise, execution will continue without applying anything extra.