Update VaultConnectionStringProvider for early parameter validation and clarify required parameters in documentation

Author: MouhsinElmajdouby

ojdbc-provider-oci/README.md

@@ -525,7 +525,7 @@ It supports both plain text and Base64-encoded `tnsnames.ora` files.
 
 This enables flexible and secure configuration for database connections using the alias names defined in your `tnsnames.ora` file.
 
-In addition to the set of common parameters, this provider also supports the parameters listed below:
+In addition to the set of common parameters, this provider also requires the parameters listed below:
 
 <table>
 <thead>

ojdbc-provider-oci/src/main/java/oracle/jdbc/provider/oci/resource/VaultConnectionStringProvider.java

@@ -106,6 +106,15 @@ public VaultConnectionStringProvider() {
   @Override
   public String getConnectionString(Map<Parameter, CharSequence> parameterValues) {
 
+    String alias;
+    try {
+      alias = parseParameterValues(parameterValues).getRequired(TNS_ALIAS);
+    } catch (IllegalStateException e) {
+      throw new IllegalArgumentException(
+              "Required parameter 'tnAlias' is missing", e
+      );
+    }
+
     // Retrieve the secret containing tnsnames.ora content from OCI Vault
     String secretValue = getVaultSecret(parameterValues)
                            .getBase64Secret();
@@ -119,15 +128,6 @@ public String getConnectionString(Map<Parameter, CharSequence> parameterValues)
       throw new IllegalStateException("Failed to read tnsnames.ora content", e);
     }
 
-    String alias;
-    try {
-      alias = parseParameterValues(parameterValues).getRequired(TNS_ALIAS);
-    } catch (IllegalStateException e) {
-      throw new IllegalArgumentException(
-              "Required parameter 'tnAlias' is missing", e
-      );
-    }
-
     String connectionString = tnsNames.getConnectionStringByAlias(alias);
     if (connectionString == null) {
       throw new IllegalArgumentException(