model: Add OperationVariable to KeyElements enum

This is not compliant with the DotAAS document, but required for
consinstency of the data model.

aas/model/__init__.py

@@ -53,6 +53,7 @@ KEY_ELEMENTS_CLASSES: Dict[type, KeyElements] = {
     Blob: KeyElements.BLOB,
     File: KeyElements.FILE,
     Operation: KeyElements.OPERATION,
+    OperationVariable: KeyElements.OPERATION_VARIABLE,
     Capability: KeyElements.CAPABILITY,
     Property: KeyElements.PROPERTY,
     MultiLanguageProperty: KeyElements.MULTI_LANGUAGE_PROPERTY,

aas/model/base.py

@@ -114,6 +114,7 @@ class KeyElements(Enum):
     FILE = 1009
     MULTI_LANGUAGE_PROPERTY = 1010
     OPERATION = 1011
+    OPERATION_VARIABLE = 1119
     PROPERTY = 1012
     RANGE = 1013
     REFERENCE_ELEMENT = 1014