fix(ingest): allow ingestion of glossary terms without nodes (#3253)

metadata-ingestion/src/datahub/ingestion/source/metadata/business_glossary.py

@@ -62,7 +62,8 @@ class BusinessGlossarySourceConfig(ConfigModel):
 
 class BusinessGlossaryConfig(DefaultConfig):
     version: str
-    nodes: List[GlossaryNodeConfig]
+    nodes: Optional[List[GlossaryNodeConfig]]
+    terms: Optional[List[GlossaryTermConfig]]
 
     @validator("version")
     def version_must_be_1(cls, v):
@@ -106,6 +107,7 @@ def get_mces(
     path: List[str] = []
     root_owners = get_owners(glossary.owners)
 
+    if glossary.nodes:
         for node in glossary.nodes:
             events += get_mces_from_node(
                 node,
@@ -114,6 +116,17 @@ def get_mces(
                 parentOwners=root_owners,
                 defaults=glossary,
             )
+
+    if glossary.terms:
+        for term in glossary.terms:
+            events += get_mces_from_term(
+                term,
+                path + [term.name],
+                parentNode=None,
+                parentOwnership=root_owners,
+                defaults=glossary,
+            )
+
     return events
 
 
@@ -171,7 +184,7 @@ def get_mces_from_node(
 def get_mces_from_term(
     glossaryTerm: GlossaryTermConfig,
     path: List[str],
-    parentNode: str,
+    parentNode: Optional[str],
     parentOwnership: models.OwnershipClass,
     defaults: DefaultConfig,
 ) -> List[models.MetadataChangeEventClass]: