Add support for escaping '---' in incoming messages

[AleksandarFaraj]

Use Case: Improve handling of incoming messages

Description:

We currently have two functions, DeserializeMessageThread and SerializeMessageThread, which are used for deserializing and serializing message threads. However, these functions do not properly escape the '---' character when new incoming messages are added to the thread.

Currently these files

Expected Behavior:

When new incoming messages are added to the message thread, the '---' character should be properly escaped to prevent any parsing issues with YAML or other serialization formats.

Steps to Reproduce:

1. Use the DeserializeMessageThread function to parse a string containing a message thread.
2. Add a new incoming message to the thread that includes the '---' character.
3. Use the SerializeMessageThread function to serialize the modified message thread back into string.
4. Attempt to deserialize the serialized string using DeserializeMessageThread.
5. Observe that the original '---' character is not properly escaped in the deserialized message.

Expected Outcome:

When the '---' character is encountered in an incoming message, it should be escaped to ensure proper handling and serialization of the message thread.

Files to Modify:

• pkg/tzapfile/tzapfile.go