[EG arch feedback] Task list

[rakshith91]

• Kill Custom Events
• Kill Deserializer
• Cloud Event make data optional
• Support Data / data_base64 (not both)data must be optional ; data_base64 is optional too data can be bytes(convert to data_base64) data and data_base64 at the same time raises.
• SystemEventMappings to SystemEvents
• change order of EG event