Updated call signature of database-info lib

refs https://github.com/TryGhost/Toolbox/issues/174

- ok, iteration 3 on how this library should work
- 95% of my use cases just need to pass an knex instance and return if
  it's mysql/sqlite
- i don't want to have to initialize the class in this library to get
  that
- this commit reworks the public interface to return a function with
  some simple `is*` functions for those uses cases, or to return the
  class otherwise

ghost/database-info/lib/database-info.js

@@ -1,4 +1,27 @@
-module.exports = class DatabaseInfo {
+/**
+ * @param {import('knex')} knex
+ */
+module.exports = (knex) => {
+    const driver = knex.client.config.client;
+
+    return {
+        /**
+         * Returns if the driver used is for SQLite
+         */
+        isSQLite: () => {
+            return ['sqlite3'].includes(driver);
+        },
+
+        /**
+         * Returns if the driver used is for MySQL
+         */
+        isMySQL: () => {
+            return ['mysql', 'mysql2'].includes(driver);
+        }
+    };
+};
+
+module.exports.DatabaseInfo = class DatabaseInfo {
     /**
      * @param {import('knex')} knex
      */
@@ -81,29 +104,4 @@ module.exports = class DatabaseInfo {
     getVersion() {
         return this._databaseDetails.version;
     }
-
-    /**
-     * Returns if the driver used is for SQLite
-     */
-    isSQLite() {
-        return ['sqlite3'].includes(this._driver);
-    }
-
-    /**
-     * Returns if the driver used is for MySQL
-     */
-    isMySQL() {
-        return ['mysql', 'mysql2'].includes(this._driver);
-    }
-
-    /**
-     * This allows you to use a different DB connection than the one we initialized the lib with
-     *
-     * @param {import('knex')} knex
-     *
-     * @returns DatabaseInfo
-     */
-    connection(knex) {
-        return new DatabaseInfo(knex);
-    }
 };