FIX Strip html tags from file upload error responses

[emteknetnz]

Fixes #915

Notes

• The max-width 50% possibly solves Error message when adding large files are not readable #895 (though it was unintentional)
• The unused messages for "file cannot be found" and "extension is not allowed" is for the DSM which does contain messages for "file size limit exceeded" and "something went wrong, please try again"

Update transifix

• Have pushed new translations to transifix (en.json has been updated in this PR, but not en.js)

New behaviour:

File Manager Gallery Server Error 413

File Manager Gallery Server Error - Non-413

Upload Field Error - Server Error 413

Upload Field Error - Server Error Non-413

Non Server Error file size too big messaging remains as is

Error can be simulated in File manager gallery by updating AssetAdmin.php

    public function apiCreateFile(HTTPRequest $request)
    {
        $this->httpError(413);

Error can be simulated in upload field by updating UploadField.php

    public function upload(HTTPRequest $request)
    {
        $this->httpError(413);

Add an upload field to Page.php

    class Page extends SiteTree
    {
        public function getCMSFields()
        {
            $uploadField = new UploadField('ABC');
            $fields = parent::getCMSFields();
            $fields->insertBefore('Title', $uploadField);
            return $fields;
        }

[Cheddam]

@emteknetnz The goal was to produce readable error messages for users, which I'd argue simply stripping the HTML tags does not achieve. With the example in the original issue, an author would now see:

413 Request Entity Too Large

The author might infer that this means their file was too big, but it's not exactly a clear description, and other errors may not fair as well. I think you'd be better off creating a map of HTTP error codes to author-readable messages and using those if the response is a string. If developers want to push through a custom error message, they need to make sure they return a valid JSON response with the errors key populated.

cc/ @silverstripeux - maybe you can collaborate on the error messaging?

[sachajudd]

Linking to #895 (comment) as I've just added some designs with four different error messages that we'd like to add in an instance that an extension is not allowed or a file is too big etc. We can come up with a few more if need be but these should allow you to cover the most common errors.

[Cheddam]

Looking good, one small recommended change.

[dhensby]

Nice work!