Integrate and adjust POST /conversations/{conversation_id}/messages endpoint

[chriskari]

Description
The Kyma Companion frontend needs to make API calls to the POST /conversations/{conversation_id}/messages endpoint in the Kyma Companion backend, to send a question and receive a streamed response.

The POC version already includes a similar API call in the file KymaCompanion/api/getChatResponse.ts. However, since the development of the POC, the API structure and requirements have been updated. This API call must be adjusted accordingly to reflect the latest backend implementation.

For detailed information on the updated API structure, refer to the API documentation.

Tasks:
The necessary adjustments include, but may not be limited to

• Endpoint and URL have changed
• Cluster authorization should already be properly added to the headers, but take a second look
• Format of request body has changed
• Format of response body has changed
• Check if the streaming of responses still works and perhaps adjust it