PADV-1558 Pull Storage definition from site configuration each time there would be a file process

[Nekenhei]

Tickets

• https://agile-jira.pearson.com/browse/PADV-1558

Description

This PR removes the storage definition from when the xblock is initialized in the platform and instead, checks the storage definition each time there would be a file action such uploads, downloads, etc.

Changes Made

• Remove storage definition prior to Xblock package being initialized
• Add storage definition pull each time a method would process a file request

How To Test

• Please follow Xblock's doc to use the SGA as it used to work, nothing shall change in terms of user experience when uploading or downloading files.
• Through the site configuration, set the following settings format using the keys provided by AWS S3 for a given bucket.

"SGA_STORAGE_SETTINGS": {
    "STORAGE_CLASS": "your.desire.storage.backend,
    "STORAGE_KWARGS":  {
        "key": "value"
    }
}

• If possible, add a print statement here and confirms that the storage definition is checked each time there would be a file process like this upload method
• Files shall be processed thru the desire storage.

Annotations

Broken dependencies and CI process

CI process of unit testing and linting is failing due to dependencies issues. It also restrict the possibility to run it locally despite of the presence of a Tox defined workflow to do so. This is because it expects the workflows and credentials from upstream, not pearson. That could be cover in future PRs, but is not the purpose of this one so it won't be reviewed.

Unit Testing

As per the missing dependencies and challenges with Tox definition, the unit testing shall be executed thru the paltaform shell. More documentation about it can be found here.