[fix] function execution events accept interfaces not strings

[ProjectBarks]

API changes [BREAKING]

In the initial implementation of this change, we assumed that the input types would always be map[string]string. However, Slack can send inputs with various types, not just strings. This update modifies the mapping to use an interface{} to handle these different input types. Additionally, the test has been updated to include an example of a real payload received from Slack to ensure proper handling of these cases.

Example

{
  "event": {
    "type": "function_executed",
    "function": {
      "id": "Fn07TRTH0EKX",
      "callback_id": "d70234",
      "title": "Test",
      "description": "Test.",
      "type": "app",
      "input_parameters": [
        {
          "type": "slack#/types/message_context",
          "name": "message_context",
          "description": "Test",
          "title": "Mesage Context",
          "is_required": true
        }
      ]
    },
    "inputs": {
      "message_context": {
        "channel_id": "C07H1ER7U66",
        "message_ts": "1733331835.871019"
      },
    },
    "function_execution_id": "Fx08387NLCNT",
    "workflow_execution_id": "Wx084BHAGCMN",
    "event_ts": "1733331846.861810"
  }
}

[calebmckay]

Code change seems simple enough.

I updated one of the automated tests to test a variety of values for the input, including the message_context type you provide in your example. You may want to pull the changes into your PR. b005e63

[ProjectBarks]

Oh I actually had cases to cover this but I guess I forgot to push. I'll incorporate b005e63 as well. Thanks!