Refactor Inter-Dactor Message Type Hierarchy

[srfc]

Refactor Inter-Dactor Message Type Hierarchy

Refactor the type hierarchy of inter-Dactor messages to improve flexibility when processing messages using pattern matching as well as to make them more manageable.

Problem Description

• Pattern matching messages within Receive methods is not very flexible because of a flat hierarchy of most message types
• Unsafe messages that are only meant for use in debugging or testing do not share a common ancestor and might be hard to keep track of so we can later warn or deprecate them for production use

Supporting Information

• Possible type hierarchy layout with a focus on improving specificity to support flexible pattern matching:

Root class	Childs	Description
akka.actor.Status	Success, Failure	Messages from the akka-framework
InternalMessageProtocol. InternalMessage	Ping, Pong, UpdateMapping, ...	Messages used internally in the adbms framework.
DefaultMessageProtocol. Status	InsertIntoRelation. Success|Failure, SelectAllFromRelation. Success|Failure	Unsafe messages, only used for testing, debugging and not meant for production.
RequestResponseProtocol. Response	<UserOp>.Success|Failure, ...	Production-grade messages defined by the developer (user of our framework). We only provide the base classes.

• RequestResponseProtocol is already on master

Related

• First came up while discussing PR Add DefaultMessagingProtocol.RelationQuery #93