Function from_protobuf_message_field

pub fn from_protobuf_message_field<'a>(
    field_desc: &FieldDescriptor,
    message: &'a DynamicMessage,
    type_expected: &DataType,
    messages_as_jsonb: &'a HashSet<String>,
) -> Result<DatumCow<'a>, AccessError>

Converts a protobuf message field to a datum.

We will get the protobuf value from the message by checking the field descriptor and correctly handling presence, then call [from_protobuf_value].