fix: Add transcription fields to session events

This change introduces `input_transcription` and `output_transcription` fields to session events, enabling the storage and retrieval of transcription data in both the database and Vertex AI session services.

Closes #3172

Co-authored-by: Hangfei Lin <hangfei@google.com>
PiperOrigin-RevId: 834366848

Author: hangfei

src/google/adk/sessions/database_session_service.py

@@ -271,6 +271,12 @@ class StorageEvent(Base):
   )
   error_message: Mapped[str] = mapped_column(String(1024), nullable=True)
   interrupted: Mapped[bool] = mapped_column(Boolean, nullable=True)
+  input_transcription: Mapped[dict[str, Any]] = mapped_column(
+      DynamicJSON, nullable=True
+  )
+  output_transcription: Mapped[dict[str, Any]] = mapped_column(
+      DynamicJSON, nullable=True
+  )
 
   storage_session: Mapped[StorageSession] = relationship(
       "StorageSession",
@@ -337,6 +343,14 @@ def from_event(cls, session: Session, event: Event) -> StorageEvent:
       storage_event.citation_metadata = event.citation_metadata.model_dump(
           exclude_none=True, mode="json"
       )
+    if event.input_transcription:
+      storage_event.input_transcription = event.input_transcription.model_dump(
+          exclude_none=True, mode="json"
+      )
+    if event.output_transcription:
+      storage_event.output_transcription = (
+          event.output_transcription.model_dump(exclude_none=True, mode="json")
+      )
     return storage_event
 
   def to_event(self) -> Event:
@@ -366,6 +380,12 @@ def to_event(self) -> Event:
         citation_metadata=_session_util.decode_model(
             self.citation_metadata, types.CitationMetadata
         ),
+        input_transcription=_session_util.decode_model(
+            self.input_transcription, types.Transcription
+        ),
+        output_transcription=_session_util.decode_model(
+            self.output_transcription, types.Transcription
+        ),
     )
 
 

tests/unittests/sessions/test_session_service.py

@@ -512,6 +512,14 @@ async def test_append_event_complete(service_type, tmp_path):
       ),
       citation_metadata=types.CitationMetadata(),
       custom_metadata={'custom_key': 'custom_value'},
+      input_transcription=types.Transcription(
+          text='input transcription',
+          finished=True,
+      ),
+      output_transcription=types.Transcription(
+          text='output transcription',
+          finished=True,
+      ),
   )
   await session_service.append_event(session=session, event=event)