also add hasIdentity to android to be consistent

Author: vricosti

android/src/main/java/com/asterinet/react/tcpsocket/SSLCertificateHelper.java

@@ -80,6 +80,30 @@ static SSLServerSocketFactory createServerSocketFactory(Context context, @NonNul
         return sslContext.getServerSocketFactory();
     }
 
+    static boolean hasIdentity(ReadableMap options) {
+        boolean hasId = false;
+        try {
+            final String keystoreName = options.hasKey("androidKeyStore") ?
+                    options.getString("androidKeyStore") : KeyStore.getDefaultType();
+            final String keyAlias = options.hasKey("keyAlias") ?
+                    options.getString("keyAlias") : "";
+
+            if (keyAlias.isEmpty()) {
+                return false;
+            }
+
+            // Get keystore instance
+            KeyStore keyStore = KeyStore.getInstance(keystoreName);
+            keyStore.load(null, null);
+
+            // Check if key entry exists with its certificate chain
+            hasId = keyStore.isKeyEntry(keyAlias);
+            return hasId;
+        } catch (Exception e) {
+            return false;
+        }
+    }
+    
     public static PrivateKey getPrivateKeyFromPEM(InputStream keyStream) {
         try (PemReader pemReader = new PemReader(new InputStreamReader(keyStream))) {
             PemObject pemObject = pemReader.readPemObject();

android/src/main/java/com/asterinet/react/tcpsocket/TcpSocketModule.java

@@ -384,6 +384,16 @@ private TcpSocketServer getTcpServer(final int id) {
         return (TcpSocketServer) socket;
     }
 
+    @SuppressWarnings("unused")
+    @ReactMethod
+    public void hasIdentity(@NonNull final ReadableMap options, Promise promise) {
+        try {
+            promise.resolve(SSLCertificateHelper.hasIdentity(options));
+        } catch (Exception e) {
+            promise.reject(e);
+        }
+    }
+
     @SuppressWarnings("unused")
     @ReactMethod
     public void getPeerCertificate(final int cId, Promise promise) {