feat: Add gzip decompression and NDJSON support for Application Insig…

[ChNorman]

Problem

The official Microsoft Application Insights SDK sends telemetry with two characteristics that azurinsight didn't handle:

1. Gzip compression: Telemetry is sent with content-encoding: gzip header
2. NDJSON format: Multiple telemetry items are batched as newline-delimited JSON, not a single JSON array

Without this support, the emulator would fail to parse Application Insights SDK telemetry with errors like:

• "SyntaxError: Unexpected non-whitespace character after JSON at position X"
• Telemetry silently lost or partially captured

Solution

Added gzip decompression middleware that:

1. Detects gzipped requests by checking content-encoding: gzip header
2. Decompresses the payload using Node.js built-in zlib.gunzipSync
3. Parses NDJSON format by splitting on newlines and parsing each line as separate JSON
4. Maintains backward compatibility by detecting single-line JSON and parsing normally
5. Positioned correctly before bodyParser middleware to intercept and pre-process the request body

Testing

• ✅ Verified with actual Application Insights SDK telemetry
• ✅ Handles both single and batched telemetry items
• ✅ Proper error handling for malformed payloads

Impact

This change makes azurinsight fully compatible with the official Microsoft Application Insights SDK, enabling developers to use it as a local development emulator without SDK-specific workarounds.

[Rahulkumar010]

Excellent contribution! 🎉

@ChNorman - Thank you for adding gzip/NDJSON support! This is a significant step makes azurinsight toward full compatibility with the official Microsoft Application Insights SDK. Great work on the implementation and testing! 👏

Really appreciate your contribution!