Add support for files upload

[ker0x]

This is a first approach to handle file upload into the app as requested in #743.

What i did:

• Create two Annotations Uploadable and UploadableField to mark an Entity has uploadable. This is very similar to what VichUploaderBundle do, but with less more feature.
• Create a Doctrine subscriber, to handle file upload on entity
• Add an interface and a trait to mark an entity as Timestampable since i need to modify at least on field to take care of the file upload.
• Update templates

What i didn't do:

• Use a third party bundle. IMO, as this is a demo application, we should first show people how to do things with the framework, before relaying on bundle.
• Add tests. Currently i don't know how to test file upload with PHPUnit, some help will be appreciate 👍
• Add the modified database because i don't know if it's fine! It could be great if Added migrations #779 can be merged. I could then add a migration file.

HOWEVER, while testing this, I encounter 2 errors:

• The first one occurs when I submit a form without adding a file. I systematically get the following error:

1/1) ErrorCall to a member function getClientOriginalName() on null
--
in RequestDataCollector.php line 64
at RequestDataCollector->collect(object(Request), object(RedirectResponse), null)in Profiler.php line 167
at Profiler->collect(object(Request), object(RedirectResponse), null)in ProfilerListener.php line 91
at ProfilerListener->onKernelResponse(object(FilterResponseEvent), 'kernel.response', object(TraceableEventDispatcher))in WrappedListener.php line 104
at WrappedListener->__invoke(object(FilterResponseEvent), 'kernel.response', object(EventDispatcher))in EventDispatcher.php line 212
at EventDispatcher->doDispatch(array(object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener),object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener)), 'kernel.response', object(FilterResponseEvent))in EventDispatcher.php line 44
at EventDispatcher->dispatch('kernel.response', object(FilterResponseEvent))in TraceableEventDispatcher.php line 141
at TraceableEventDispatcher->dispatch('kernel.response', object(FilterResponseEvent))in HttpKernel.php line 189
at HttpKernel->filterResponse(object(RedirectResponse), object(Request), 1)in HttpKernel.php line 171
at HttpKernel->handleRaw(object(Request), 1)in HttpKernel.php line 67
at HttpKernel->handle(object(Request), 1, true)in Kernel.php line 188
at Kernel->handle(object(Request))in index.php line 37

• Second one happen when i submit the form with a file:

(1/2) FileNotFoundExceptionThe file "/tmp/phpoXdkSq" does not exist
--
in MimeTypeGuesser.php line 116
at MimeTypeGuesser->guess('/tmp/phpoXdkSq')in File.php line 79
at File->getMimeType()in RequestDataCollector.php line 65
at RequestDataCollector->collect(object(Request), object(RedirectResponse), null)in Profiler.php line 167
at Profiler->collect(object(Request), object(RedirectResponse), null)in ProfilerListener.php line 91
at ProfilerListener->onKernelResponse(object(FilterResponseEvent), 'kernel.response', object(TraceableEventDispatcher))in WrappedListener.php line 104
at WrappedListener->__invoke(object(FilterResponseEvent), 'kernel.response', object(EventDispatcher))in EventDispatcher.php line 212
at EventDispatcher->doDispatch(array(object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener),object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener), object(WrappedListener)), 'kernel.response', object(FilterResponseEvent))in EventDispatcher.php line 44
at EventDispatcher->dispatch('kernel.response', object(FilterResponseEvent))in TraceableEventDispatcher.php line 141
at TraceableEventDispatcher->dispatch('kernel.response', object(FilterResponseEvent))in HttpKernel.php line 189
at HttpKernel->filterResponse(object(RedirectResponse), object(Request), 1)in HttpKernel.php line 171
at HttpKernel->handleRaw(object(Request), 1)in HttpKernel.php line 67
at HttpKernel->handle(object(Request), 1, true)in Kernel.php line 188
at Kernel->handle(object(Request))in index.php line 37

The file is correctly uploaded and the field in the database is filled in 😞

I have the same upload implementation in another project, on Symfony 4.1.6 and everything works fine. If anyone has any idea what's wrong, I'm interested. I tested it on the internal PHP server and on a VM with Homestead, I have the same errors.

[javiereguiluz]

Romain, I'm sorry because of the lack of feedback to this contribution of yours. I want to apologize because I handled this wrongly. I should have replied earlier and say that this was probably a bit too much for the demo application. In any case, thanks for your contribution 🙏