Add gzip compression using Compression Streams API

[raikasdev]

Problem

Adds GZIP compression support for json capturemode

Closes #254

Changes

Simple wrapper around CompressionStream and a function to check if the class is available

Release info Sub-libraries affected

Bump level

• Major
• Minor
• Patch

Libraries affected

• All of them
• posthog-web
• posthog-node
• posthog-ai
• posthog-react-native

Changelog notes

• Added support for GZIP compression in posthog-js-lite using Web APIs

[greptile-apps]

PR Summary

Added GZIP compression support for JSON capture mode using the Compression Streams API, improving data transmission efficiency for large payloads.

• Added gzip.ts with feature detection and compression functionality using CompressionStream
• Modified batch endpoint URL to include ?compression=gzip-js parameter when GZIP is enabled
• Updated PostHogFetchOptions type to support Blob body for compressed data
• Added runtime check via isGzipSupported() to gracefully handle environments without compression support
• Set Content-Type header to text/plain for GZIP compressed requests

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[marandaneto]

@raikasdev the remote config/decide API will return supportedCompression, we need to check if its acceptable on the server side as well.
you can check the PostHogDecideResponse object.
and how this is used on the JS SDK: https://github.com/PostHog/posthog-js/blob/db26fffea82197b74e5f1f3c0b240b00d0e363e8/src/types.ts#L1255-L1258

[marandaneto]

@raikasdev once you fix tests (maybe you have to forcefully disable compression in tests)/lint I can test it out.
some unit tests would be awesome as well regarding the supported compressions and cangzip

[raikasdev]

Fixed tests requiring JSON bodies and added few tests for gzip compress using Node's builtin gzip (via node:zlib)

[marandaneto]

posthog-js-lite/posthog-core/src/index.ts

Line 854 in df41c7b

body: `data=${encodeURIComponent(LZString.compressToBase64(payload))}&compression=lz64`,

on this line we should also check for disableCompression and supportedCompression

[raikasdev]

Test should be fixed, weird that it worked locally without the import 😄. I'll look at the comments later today

[raikasdev]

@marandaneto If lz64 is getting deprecated should the captureMode form also be using gzip if it is available in the runtime?

[marandaneto]

@marandaneto If lz64 is getting deprecated should the captureMode form also be using gzip if it is available in the runtime?

this will be addressed later on with another issue/PR #483
lets keep this one simple for now.

[marandaneto]

@raikasdev thanks
one last comment and fix the lint and GG

[raikasdev]

Weird, locally prettier doesn't show anything 🤔

[marandaneto]

Weird, locally prettier doesn't show anything 🤔

probably versioning, lets see if this helps 272e099 (#481)