Update Error/Logging functionalities

[Elfangor93]

This PR fixes and improves the error and logging functionities provided by the JoomGallery extension class. The following methods are available:

// Add debug message
setDebug($txt, $new_line=true, $margin_top=false, $log=false, $name=null)

// Add warning message
setWarning($txt, $new_line=true, $margin_top=false, $log=false, $name=null)

// Add error message
setError($txt, $new_line=true, $margin_top=false, $log=true, $name=null)

// Add a message to a logging file
setLog($txt, $priority = 8, $name = null)

With the argument $log you can activate to add also a logging entry. So the message will be outputted as well as logged. With $name you can choose the filename of the logging file where to output. The default file is com_joomgallery.log.php. If you add a logging name the file will look like com_joomgallery.name.log.php.

How to test this PR

Scenario 1 (manually set an error)

Edit a HtmlView.php file of your choice. Add the following line:

$this->component->setError('Your error message');

Activate "Debug System" in the Joomla global configuration. Access the view you edited.

You should get the error message as a bootstrap alert box

Additionally you get the message in the Joomla internal debugging console

And you should see a file in your Joomla log directory called com_joomgallery.log.php where you find the error message

Scenario 2 (error during upload)

Upload two faulty images via the uppy uploader. You should see a file in your Joomla log directory called com_joomgallery.log.php where you find the error message thrown from uploading the faulty images.

Scenario 3 (error during migration)

Force an error during migration in step 3 of the migration manager. You should see a file in your Joomla log directory called com_joomgallery.log.php where you find the error message thrown from uploading the faulty images.

[MrMusic]

I have tested this PR ✅ successfully. Thank you very much.

[Elfangor93]

I will merge this PR after #215 is merged.