Ensure JSON keys are in double quotes on updating JSON columns.

- Currently if your JSON keys have a dash, the update fails due to this issue https://bugs.mysql.com/bug.php?id=81896
- this change ensures the keys are within double quotes
- before: “$.foo-bar”
- after: '$."foo-bar"'
- I changed the test to reflect the new format

Author: lucidlogic

src/Illuminate/Database/Query/Grammars/MySqlGrammar.php

@@ -163,7 +163,7 @@ protected function compileJsonUpdateColumn($key, JsonExpression $value)
 
         $field = $this->wrapValue(array_shift($path));
 
-        $accessor = '"$.'.implode('.', $path).'"';
+        $accessor = "'$.\"".implode('.', $path)."\"'";
 
         return "{$field} = json_set({$field}, {$accessor}, {$value->getValue()})";
     }

tests/Database/DatabaseQueryBuilderTest.php

@@ -1676,7 +1676,7 @@ public function testMySqlUpdateWrappingJson()
         $connection->expects($this->once())
                     ->method('update')
                     ->with(
-                        'update `users` set `name` = json_set(`name`, "$.first_name", ?), `name` = json_set(`name`, "$.last_name", ?) where `active` = ?',
+                        'update `users` set `name` = json_set(`name`, \'$."first_name"\', ?), `name` = json_set(`name`, \'$."last_name"\', ?) where `active` = ?',
                         ['John', 'Doe', 1]
                     );
 
@@ -1694,7 +1694,7 @@ public function testMySqlUpdateWithJsonRemovesBindingsCorrectly()
         $connection->shouldReceive('update')
                     ->once()
                     ->with(
-                        'update `users` set `options` = json_set(`options`, "$.enable", false), `updated_at` = ? where `id` = ?',
+                        'update `users` set `options` = json_set(`options`, \'$."enable"\', false), `updated_at` = ? where `id` = ?',
                         ['2015-05-26 22:02:06', 0]
                     );
         $builder = new Builder($connection, $grammar, $processor);