fix: set canonical User-Agent header format

[gjtorikian]

Summary

The Tesla middleware was sending no User-Agent header on outgoing requests. This adds one in the canonical WorkOS SDK format: workos-elixir/{VERSION}, with the version pulled from the application spec.

Test plan

• Manual verification: Application.spec(:workos, :vsn) returns the charlist version (e.g. ~c"1.2.1"), and Elixir's String.Chars.List implementation converts charlists to a binary on #{} interpolation, so the resulting header value is workos-elixir/1.2.1.
• Confirm User-Agent on a real outgoing request

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

This PR adds a User-Agent: workos-elixir/{VERSION} header to all outgoing Tesla HTTP requests by introducing a private user_agent/0 helper that reads the version at runtime via Application.spec(:workos, :vsn). The change is minimal and correct — charlist interpolation in Elixir produces the expected binary string.

Confidence Score: 4/5

Safe to merge; only a P2 nil-safety suggestion on the version lookup.

The change is small and focused with no logic errors or security concerns. The sole finding is a P2 style suggestion to guard against a nil version string in edge-case environments.

No files require special attention.

Important Files Changed

Filename	Overview
lib/workos/client/tesla_client.ex	Adds User-Agent: workos-elixir/{VERSION} header via a new private user_agent/0 helper; minor concern around nil-safety of Application.spec/2.

Sequence Diagram

sequenceDiagram
    participant Caller
    participant TeslaClient
    participant Tesla
    participant WorkOS API

    Caller->>TeslaClient: request(client, opts)
    TeslaClient->>TeslaClient: user_agent() → "workos-elixir/1.2.1"
    TeslaClient->>Tesla: Tesla.client([..., Headers: [Authorization, User-Agent]])
    Tesla->>WorkOS API: HTTP request with User-Agent: workos-elixir/1.2.1
    WorkOS API-->>Tesla: Response
    Tesla-->>Caller: {:ok, response}

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[greptile-apps]

Guard against nil version

Application.spec(:workos, :vsn) returns nil when the application is not loaded (e.g. in certain test setups or as a library dependency that hasn't started). Interpolating nil yields "workos-elixir/", which is a malformed User-Agent. A compile-time attribute or a runtime fallback would be safer.

Suggested change

	"workos-elixir/#{Application.spec(:workos, :vsn)}"
	version = Application.spec(:workos, :vsn) || "unknown"
	"workos-elixir/#{version}"