Address PR feedback

Author: lahirumaramba

src/main/java/com/google/firebase/appcheck/AppCheckErrorCode.java

@@ -29,10 +29,5 @@ public enum AppCheckErrorCode {
   /**
    * Internal server error.
    */
-  INTERNAL,
-
-  /**
-   * User is not authenticated.
-   */
-  UNAUTHENTICATED,
+  INTERNAL
 }

src/main/java/com/google/firebase/appcheck/AppCheckTokenVerifier.java

@@ -68,7 +68,7 @@ private AppCheckTokenVerifier(Builder builder) {
   DecodedAppCheckToken verifyToken(String token) throws FirebaseAppCheckException {
     SignedJWT signedJWT;
     JWTClaimsSet claimsSet;
-    String scopedProjectId = String.format("projects/%s", projectId);
+    String projectName = String.format("projects/%s", projectId);
     String projectIdMatchMessage = " Make sure the App Check token comes from the same "
             + "Firebase project as the service account used to authenticate this SDK.";
 
@@ -88,10 +88,10 @@ DecodedAppCheckToken verifyToken(String token) throws FirebaseAppCheckException
     } else if (!signedJWT.getHeader().getType().getType().equals("JWT")) {
       errorMessage = String.format("The provided App Check token has invalid type header."
               + "Expected %s but got %s", "JWT", signedJWT.getHeader().getType().getType());
-    } else if (!claimsSet.getAudience().contains(scopedProjectId)) {
+    } else if (!claimsSet.getAudience().contains(projectName)) {
       errorMessage = String.format("The provided App Check token has incorrect 'aud' (audience) "
               + "claim. Expected %s but got %s. %s",
-              scopedProjectId, claimsSet.getAudience().toString(), projectIdMatchMessage);
+              projectName, claimsSet.getAudience().toString(), projectIdMatchMessage);
     } else if (!claimsSet.getIssuer().startsWith(APP_CHECK_ISSUER)) {
       errorMessage = "invalid iss";
     } else if (claimsSet.getSubject().isEmpty()) {

src/main/java/com/google/firebase/appcheck/DecodedAppCheckToken.java

@@ -52,13 +52,13 @@ public String getAudience() {
   }
 
   /** Returns the Expiration Time for this token. */
-  public String getExpirationTime() {
-    return (String) claims.get("exp");
+  public Long getExpirationTime() {
+    return (Long) claims.get("exp");
   }
 
   /** Returns the Issued At for this token. */
-  public String getIssuedAt() {
-    return (String) claims.get("iat");
+  public Long getIssuedAt() {
+    return (Long) claims.get("iat");
   }
 
   /** Returns a map of all the claims on this token. */