The PATCH method for the entry should only update what user sent to us and not the whole entry as it was before.
Also, sending tags when patching an entry will now remove all current tags & assocatied new ones.
Instead of saving the value of each field right into the content without any validation, it seems better to validate them.
This might sounds obvious now we say that.
This commit also decouples the "import" and "update" functions inside
ContentProxy. If a content array is available, it must be passed to the
new importEntry method.
Objects are always passed by reference, so it doesn't make sense to
return an object which is passed by reference as it will always be the
same object. This change makes the code a bit more readable.
If the website doesn't provide an og_image, the value will be false and so it'll be saved like that in the database.
We prefer to leave it as null instead of false.
