feat: add github oauth

frontend/pages/auth/components/login-github.tsx

@@ -0,0 +1,42 @@
+import React, { useEffect, useMemo } from "react";
+import { makeRedirectUri, useAuthRequest } from "expo-auth-session";
+import appConfig from "@/app.json";
+import { Button } from "tamagui";
+import { useOAuthCallback } from "../hooks";
+import { useServerConfig } from "@/hooks/useServerConfig";
+
+const LoginGithubButton = () => {
+  const { data: clientId } = useServerConfig("github_client_id");
+  const discovery = useMemo(() => {
+    return {
+      authorizationEndpoint: "https://github.com/login/oauth/authorize",
+      tokenEndpoint: "https://github.com/login/oauth/access_token",
+      revocationEndpoint: `https://github.com/settings/connections/applications/${clientId}`,
+    };
+  }, [clientId]);
+  const oauth = useOAuthCallback("github");
+
+  const [request, response, promptAsync] = useAuthRequest(
+    {
+      clientId: clientId,
+      scopes: ["identity"],
+      redirectUri: makeRedirectUri({ scheme: appConfig.scheme }),
+    },
+    discovery
+  );
+
+  useEffect(() => {
+    if (response?.type === "success") {
+      const { code } = response.params;
+      oauth.mutate(code);
+    }
+  }, [response]);
+
+  return (
+    <Button disabled={!request} onPress={() => promptAsync()}>
+      Login with Github
+    </Button>
+  );
+};
+
+export default LoginGithubButton;