Polishing.

Introduce convenience factory method to convert a VaultToken into LoginToken.

See gh-159.

spring-vault-core/src/main/java/org/springframework/vault/authentication/LoginToken.java

@@ -163,6 +163,21 @@ public class LoginToken extends VaultToken {
 		return new LoginToken(token, Duration.ofSeconds(leaseDurationSeconds), true);
 	}
 
+	/**
+	 * Create a new renewable {@link LoginToken} with a {@code leaseDurationSeconds}.
+	 *
+	 * @param token must not be {@literal null}.
+	 * @param leaseDuration the lease duration, must not be {@literal null} or negative.
+	 * @return the created {@link VaultToken}
+	 * @since 2.0
+	 */
+	public static LoginToken renewable(VaultToken token, Duration leaseDuration) {
+
+		Assert.notNull(token, "Token must not be null");
+
+		return renewable(token.toCharArray(), leaseDuration);
+	}
+
 	/**
 	 * Create a new renewable {@link LoginToken} with a {@code leaseDurationSeconds}.
 	 *

spring-vault-core/src/main/java/org/springframework/vault/authentication/LoginTokenAdapter.java

@@ -108,7 +108,7 @@ public class LoginTokenAdapter implements ClientAuthentication {
 		}
 	}
 
-	private static Duration getLeaseDuration(@Nullable Number ttl) {
+	static Duration getLeaseDuration(@Nullable Number ttl) {
 		return ttl == null ? Duration.ZERO : Duration.ofSeconds(ttl.longValue());
 	}
 }