Improves error handling, logging, and messaging in Slack plugin

[mvilanova]

This pull request includes several updates to the dispatch_slack plugin to improve the handling of case messages, specifically around signal analysis and action buttons. The most important changes include updating function arguments to use case objects instead of case_id, enhancing the GenAI signal analysis message generation, and improving error handling and logging.

Updates to function arguments and imports:

• Changed function arguments from case_id to case to streamline data handling and improve code readability in create_signal_message, create_action_buttons_message, and create_genai_signal_analysis_message functions. (src/dispatch/plugins/dispatch_slack/case/messages.py) [1] [2] [3]
• Added case_service import to facilitate fetching case details. (src/dispatch/plugins/dispatch_slack/case/messages.py)

Enhancements to GenAI signal analysis:

• Improved the GenAI signal analysis message generation by checking if signal instances exist and if the GenAI feature is enabled for the detection. Added detailed logging and error handling for better traceability. (src/dispatch/plugins/dispatch_slack/case/messages.py) [1] [2] [3]
• Enhanced the generation of historical context by increasing the number of relevant messages fetched and included in the analysis. (src/dispatch/plugins/dispatch_slack/case/messages.py)
• Added checks for the GenAI plugin's availability and prompt before generating the analysis. Improved logging to capture the plugin's response. (src/dispatch/plugins/dispatch_slack/case/messages.py)

Error handling and logging improvements:

• Improved error handling and logging for GenAI signal analysis message generation to ensure any issues are properly logged and communicated. (src/dispatch/plugins/dispatch_slack/case/messages.py) [1] [2]
• Updated the create_threaded function to handle potential errors when generating GenAI signal analysis messages and ensure the correct timestamp is used. (src/dispatch/plugins/dispatch_slack/plugin.py) [1] [2] [3]