Upgrade to Laravel 8.x and some features

[steffjenl]

Merged https://github.com/steffjenl/okazanta to 2.5 branch, mean reasen is to get security patches and PHP 8.1 support

• Upgrade to Laravel 8.x
• Upgrade PHP to 7.3 till 8.1 support
• RSS Support
• ICAL Attachment on Schedule notification
• Dutch lang files updated
• New Laravel Notification templates (Copyright and title are now the site name)
• Every notification are using now the queue
• SQL Injection protection for API
• CORS protection standard enabled

TO DO:

• Twitter, Badger, Emoij packages must first released and changed in composer.json

[jbrooksuk]

@steffjenl thanks for this. However, this is quite a lot to review in one go. Can you split this into multiple PRs and build on each one, please?

[steffjenl]

I will look at it in the end off october. For the Larvavel 6.x to Larvel 8.x upgrade you must change a lot files at once to get the tests green and all the functionality working. For now I will close the PR @jbrooksuk