fix: store HTTP response body as raw string

[alexluong]

Summary

• Stop parsing JSON response bodies into map[string]interface{} in ParseHTTPResponse
• Body is now always stored as a raw string regardless of content type
• Migrate attempts.response_data column from JSONB to TEXT (migration 000009)
• Consistent with how we treat event.Data (raw bytes, no parsing) after feat: change Event.Data to json.RawMessage to preserve JSON key order #714 / fix: migrate PG event data columns from JSONB to TEXT #718

Context

After #714 switched Event.Data to json.RawMessage and #718 migrated PG columns from JSONB to TEXT, response data is the remaining place where we parse and restructure data rather than preserving it verbatim.

Currently, when a destination returns a JSON response, we unmarshal the body into a Go map. This:

1. Loses the original key ordering
2. Treats JSON and non-JSON responses inconsistently

This change stores the body as-is, matching our approach for event data integrity.

Breaking changes

API: response_data.body is now always a string, even when the destination returns application/json.

Before — JSON response body was a parsed object:

{
  "status": 200,
  "body": {
    "id": "usr_123",
    "status": "created",
    "metadata": { "source": "api" }
  }
}

After — body is the raw response string:

{
  "status": 200,
  "body": "{\"id\":\"usr_123\",\"status\":\"created\",\"metadata\":{\"source\":\"api\"}}"
}

Non-JSON responses are unchanged (already stored as strings).

Database: attempts.response_data column is migrated from JSONB to TEXT (migration 000009). Serialization is now handled in application code, consistent with events.data and attempts.event_data.

🤖 Generated with Claude Code

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