add snippet for manual oidc sign-in (#413)

Author: thatfiredev

auth/app/src/main/java/com/google/firebase/quickstart/auth/GenericIdpActivity.java

@@ -6,6 +6,7 @@
 import com.google.android.gms.tasks.OnFailureListener;
 import com.google.android.gms.tasks.OnSuccessListener;
 import com.google.android.gms.tasks.Task;
+import com.google.firebase.auth.AuthCredential;
 import com.google.firebase.auth.AuthResult;
 import com.google.firebase.auth.FirebaseAuth;
 import com.google.firebase.auth.FirebaseUser;
@@ -261,4 +262,30 @@ public void onFailure(@NonNull Exception e) {
                         });
         // [END auth_oidc_provider_reauth]
     }
+
+    public void manuallySignIn(String idToken) {
+        // [START auth_oidc_provider_signin_manual]
+        AuthCredential credential = OAuthProvider
+                .newCredentialBuilder("oidc.example-provider")  // As registered in Firebase console.
+                .setIdToken(idToken)  // ID token from OpenID Connect flow.
+                .build();
+        FirebaseAuth.getInstance()
+                .signInWithCredential(credential)
+                .addOnSuccessListener(new OnSuccessListener<AuthResult>() {
+                    @Override
+                    public void onSuccess(AuthResult authResult) {
+                        // User is signed in.
+
+                        // IdP data available in:
+                        //    authResult.getAdditionalUserInfo().getProfile()
+                    }
+                })
+                .addOnFailureListener(new OnFailureListener() {
+                    @Override
+                    public void onFailure(@NonNull Exception e) {
+                        // Handle failure.
+                    }
+                });
+        // [END auth_oidc_provider_signin_manual]
+    }
 }

auth/app/src/main/java/com/google/firebase/quickstart/auth/kotlin/GenericIdpActivity.kt

@@ -3,6 +3,9 @@ package com.google.firebase.quickstart.auth.kotlin
 import androidx.appcompat.app.AppCompatActivity
 import com.google.firebase.auth.FirebaseAuth
 import com.google.firebase.auth.OAuthProvider
+import com.google.firebase.auth.ktx.auth
+import com.google.firebase.auth.ktx.oAuthCredential
+import com.google.firebase.ktx.Firebase
 
 class GenericIdpActivity : AppCompatActivity() {
 
@@ -188,4 +191,24 @@ class GenericIdpActivity : AppCompatActivity() {
             }
         // [END auth_oidc_provider_reauth]
     }
+
+    fun manuallySignIn(idToken: String) {
+        // [START auth_oidc_provider_signin_manual]
+        val providerId = "oidc.example-provider" // As registered in Firebase console.
+        val credential = oAuthCredential(providerId) {
+            setIdToken(idToken) // ID token from OpenID Connect flow.
+        }
+        Firebase.auth
+            .signInWithCredential(credential)
+            .addOnSuccessListener { authResult ->
+                // User is signed in.
+
+                // IdP data available in:
+                //    authResult.additionalUserInfo.profile
+            }
+            .addOnFailureListener { e ->
+                // Handle failure.
+            }
+        // [END auth_oidc_provider_signin_manual]
+    }
 }