Support Faraday 2 alongside 1.x

[Tonkpils]

What

Makes elastomer-client work on both Faraday 1.x and 2.x

Why

elastomer-client's faraday constraint was already open (>= 0.17), but it depended on the deprecated faraday_middleware, which pins faraday to ~> 1.0. The only thing actually used from it was the :gzip middleware.

Changes

• Swap faraday_middleware for faraday-gzip (works on both 1.x and 2.x). It registers :gzip on Faraday::Request, so conn.use(:gzip) becomes conn.request(:gzip).
• Faraday 2 removed Connection#token_auth/#basic_auth. The :authorization middleware isn't a clean swap (its API and header output differ across majors), so set the Authorization header directly. Verified byte-identical to Faraday 1.x's token_auth/basic_auth output (Token token="..." / Basic <base64>).
• gemspec: faraday >= 1.0, < 3, drop faraday_middleware, add faraday-gzip. Bump to 6.3.0.
• All 5 custom middleware already use Faraday 2 patterns (Faraday::Middleware + @app.call/on_complete), no changes needed.

Test changes (necessitated by the above)

• Auth tests spied on the removed token_auth/basic_auth methods — now assert the resulting Authorization header (no live server needed). The spy dev dep is no longer used.
• The block-config test referenced the gone FaradayMiddleware::Instrumentation — swapped for elastomer's own :opaque_id.
• The retry test looked up the relocated retry class via the middleware registry.

CI

Added a Faraday 1.x / 2.x gemfile matrix so both majors are tested against the same ES versions.

[Copilot]

Pull request overview

Updates elastomer-client to support both Faraday 1.x and 2.x by removing the deprecated faraday_middleware dependency and adjusting connection/auth setup and tests/CI to be compatible across both majors.

Changes:

• Replace faraday_middleware with faraday-gzip and update gzip middleware wiring.
• Remove usage of token_auth / basic_auth helpers and set Authorization header directly for consistent output across Faraday 1/2.
• Add CI Gemfile matrix (Faraday 1.x + 2.x) and adjust tests to assert headers/lookup middleware appropriately.

Show a summary per file

File	Description
lib/elastomer_client/client.rb	Switch gzip middleware dependency/usage and implement cross-version auth header handling.
test/client_test.rb	Update tests to validate Authorization header output and Faraday 1/2 retry middleware lookup; swap removed instrumentation reference.
elastomer-client.gemspec	Constrain Faraday to >= 1.0, < 3 and replace faraday_middleware with faraday-gzip.
Gemfile	Add faraday-retry for Faraday 2 default dev/test bundle; drop unused spy.
gemfiles/faraday_1.gemfile	Add a dedicated Faraday 1.x test Gemfile for CI matrix.
gemfiles/faraday_2.gemfile	Add a dedicated Faraday 2.x test Gemfile (including faraday-retry).
.github/workflows/main.yml	Run CI against both Faraday majors via BUNDLE_GEMFILE matrix.
lib/elastomer_client/version.rb	Bump version to 6.3.0.
CHANGELOG.md	Document the Faraday 2 compatibility release.
.gitignore	Ignore generated per-gemfile lockfiles (gemfiles/*.lock).

Copilot's findings

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• Files reviewed: 9/10 changed files
• Comments generated: 0

[tomthorogood]

@Tonkpils Thanks for doing this; we will also need to update github/github to use the new version of this client once it is released. I can take care of that, just wanted to let you know it won't flow in automatically on merge. ❤️