feat(auth-oauth2): custom parameters for authorization, token, and refresh requests (#629)

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

plugins/auth-oauth2/tests/fetchAccessToken.test.ts

@@ -36,6 +36,12 @@ function formValue(httpRequest: Partial<HttpRequest>, name: string) {
   return (httpRequest.body?.form ?? []).find((p: { name: string }) => p.name === name)?.value;
 }
 
+function headerValue(httpRequest: Partial<HttpRequest>, name: string) {
+  return (httpRequest.headers ?? []).find(
+    (h: { name: string }) => h.name.toLowerCase() === name.toLowerCase(),
+  )?.value;
+}
+
 const baseArgs = {
   clientId: "client-123",
   accessTokenUrl: "https://auth.example.com/token",
@@ -91,3 +97,102 @@ describe("fetchAccessToken scope handling", () => {
     expect(formNames(sent[0]!)).not.toContain("scope");
   });
 });
+
+describe("fetchAccessToken custom parameters", () => {
+  test("sends a custom header with the token request", async () => {
+    const { ctx, sent } = createMockContext();
+
+    await fetchAccessToken(ctx, {
+      ...baseArgs,
+      grantType: "authorization_code",
+      custom: {
+        headers: [{ name: "Origin", value: "https://app.example.com" }],
+        body: [],
+      },
+    });
+
+    expect(headerValue(sent[0]!, "Origin")).toBe("https://app.example.com");
+  });
+
+  test("keeps the generated headers that are not overridden", async () => {
+    const { ctx, sent } = createMockContext();
+
+    await fetchAccessToken(ctx, {
+      ...baseArgs,
+      grantType: "client_credentials",
+      credentialsInBody: false,
+      custom: {
+        headers: [{ name: "Origin", value: "https://app.example.com" }],
+        body: [],
+      },
+    });
+
+    expect(headerValue(sent[0]!, "User-Agent")).toBe("yaak");
+    expect(headerValue(sent[0]!, "Content-Type")).toBe("application/x-www-form-urlencoded");
+    expect(headerValue(sent[0]!, "Accept")).toBe(
+      "application/x-www-form-urlencoded, application/json",
+    );
+    // Basic credentials still go out untouched
+    expect(headerValue(sent[0]!, "Authorization")).toMatch(/^Basic /);
+  });
+
+  test("replaces a generated header of the same name", async () => {
+    const { ctx, sent } = createMockContext();
+
+    await fetchAccessToken(ctx, {
+      ...baseArgs,
+      grantType: "client_credentials",
+      credentialsInBody: false,
+      custom: {
+        headers: [
+          { name: "content-type", value: "application/json" },
+          { name: "Authorization", value: "Custom abc123" },
+        ],
+        body: [],
+      },
+    });
+
+    const contentTypes = (sent[0]!.headers ?? []).filter(
+      (h: { name: string }) => h.name.toLowerCase() === "content-type",
+    );
+    expect(contentTypes).toEqual([{ name: "content-type", value: "application/json" }]);
+    expect(headerValue(sent[0]!, "Authorization")).toBe("Custom abc123");
+  });
+
+  test("sends custom body params in the form-encoded body", async () => {
+    const { ctx, sent } = createMockContext();
+
+    await fetchAccessToken(ctx, {
+      ...baseArgs,
+      grantType: "password",
+      params: [{ name: "username", value: "alice" }],
+      custom: {
+        headers: [],
+        body: [{ name: "realm", value: "employees" }],
+      },
+    });
+
+    expect(sent[0]!.bodyType).toBe("application/x-www-form-urlencoded");
+    expect(formValue(sent[0]!, "realm")).toBe("employees");
+    // Generated params survive alongside it
+    expect(formValue(sent[0]!, "grant_type")).toBe("password");
+    expect(formValue(sent[0]!, "username")).toBe("alice");
+    expect(formValue(sent[0]!, "client_id")).toBe("client-123");
+  });
+
+  test("replaces a generated body param of the same name", async () => {
+    const { ctx, sent } = createMockContext();
+
+    await fetchAccessToken(ctx, {
+      ...baseArgs,
+      grantType: "client_credentials",
+      custom: {
+        headers: [],
+        body: [{ name: "scope", value: "custom-scope" }],
+      },
+    });
+
+    expect(formNames(sent[0]!).filter((n: string) => n === "scope")).toHaveLength(1);
+    expect(formValue(sent[0]!, "scope")).toBe("custom-scope");
+  });
+});