Support the --ssl and --skip-ssl flags in wp db import

`wp db import` (and other commands that build their MySQL invocation via
`DB_Command::get_mysql_args()`, such as `wp db query`) run the associative
arguments through an allow-list of valid MySQL client options. That list
already contained `ssl-mode` and every `ssl-*` certificate option, but was
missing the plain on/off toggles `ssl` and `skip-ssl`.

As a result, `wp db import --ssl` silently dropped the flag and connected
without SSL, while `wp db cli --ssl` worked because it passes the arguments
straight through. This produced confusing failures such as
"Error: Failed to get current SQL modes. Reason: ERROR 1045 (28000):
Access denied" against servers that require SSL.

Add `ssl` and `skip-ssl` to the allow-list so both are forwarded to the
MySQL/MariaDB client, matching `wp db cli` behaviour. A Behat scenario
asserts the flag now appears in the final MySQL command.

Fixes #218.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: TowyTowy

features/db-import.feature

@@ -106,6 +106,25 @@ Feature: Import a WordPress database
       Success: Imported from 'debug.sql'.
       """
 
+  # Regression test for https://github.com/wp-cli/db-command/issues/218
+  # The `--ssl` flag used to be silently dropped by `get_mysql_args()` because it
+  # was missing from the list of allowed MySQL client options, so `wp db import
+  # --ssl` connected without SSL. Assert the flag is now forwarded to the MySQL
+  # command (visible in the debug output before the connection is attempted).
+  # SQLite does not use the MySQL client, hence the tag.
+  @require-mysql-or-mariadb
+  Scenario: Import forwards the --ssl flag to the MySQL client
+    Given a WP install
+
+    When I run `wp db export wp_cli_test.sql`
+    Then the wp_cli_test.sql file should exist
+
+    When I try `wp db import wp_cli_test.sql --ssl --debug`
+    Then STDERR should contain:
+      """
+      --ssl
+      """
+
   # For SQLite this would fail at the `wp db create` step
   # because of the missing plugin/drop-in.
   @require-mysql-or-mariadb

src/DB_Command.php

@@ -2231,7 +2231,9 @@ private static function get_mysql_args( $assoc_args ) {
 			'skip-named-commands',
 			'skip-pager',
 			'skip-reconnect',
+			'skip-ssl',
 			'socket',
+			'ssl',
 			'ssl-ca',
 			'ssl-capath',
 			'ssl-cert',