Move to full chat prompt

[renehonig]

Describe the background of your pull request

This PR move to the full implementation of the ChatPrompt, including the chat history. It should also make the engine more conversational in preparation for the implementation of follow up questions on the client.

Governance

• Documentation is added
• Test cases are added or updated

By submitting this pull request I confirm that:

• I've read the contributing document https://github.com/alkem-io/.github/blob/master/CONTRIBUTING.md.
• I've read and understand the Code of Conduct https://github.com/alkem-io/.github/blob/master/CODE_OF_CONDUCT.md.
• I understand that any contributions or suggestions I made may make it into the actual code. I've read the License
  https://github.com/alkem-io/Coordination/blob/master/LICENSE.
• I understand that submitting the pull request requires agreeing to and signing the contributor license agreement.