Values:
UPDATE_TYPE_UNSPECIFIED (0):
Defaults to full replace behavior, ie. FULL_REPLACE.
UPDATE_TYPE_REPLACE (1):
Fully replace all the fields. Any field masks
will be ignored.
UPDATE_TYPE_MERGE (2):
Merge the fields into the existing entities.
UPDATE_TYPE_INSERT_PROPERTIES_BY_NAMES (3):
Inserts the properties by names.
UPDATE_TYPE_REPLACE_PROPERTIES_BY_NAMES (4):
Replace the properties by names.
UPDATE_TYPE_DELETE_PROPERTIES_BY_NAMES (5):
Delete the properties by names.
