[SPARK-51490] Support iOS, watchOS, and tvOS

Author: dongjoon-hyun

Sources/SparkConnect/SparkSession.swift

@@ -45,7 +45,13 @@ public actor SparkSession {
   ///   - userID: an optional user ID. If absent, `SPARK_USER` environment or ``ProcessInfo.processInfo.userName`` is used.
   init(_ connection: String, _ userID: String? = nil) {
     let processInfo = ProcessInfo.processInfo
+#if os(iOS) || os(watchOS) || os(tvOS)
+    let userName = processInfo.environment["SPARK_USER"] ?? ""
+#elseif os(macOS) || os(Linux)
     let userName = processInfo.environment["SPARK_USER"] ?? processInfo.userName
+#else
+    assert(false, "Unsupported platform")
+#endif
     self.client = SparkConnectClient(remote: connection, user: userID ?? userName)
     self.conf = RuntimeConf(self.client)
   }