Check for identity before identifier param in direct-upload

Description

Adds the identity param in addition to the old identifier for better API compliance.

The old parameter is still supported, but identity has precedence.

Changes

• identifier is now only used if identity is not present

Additions

• the identity parameter

Test and Review

Resolves #254 (closed)

To be filled in by the reviewers

• All of the methods are commented to expectation

• The methods are tested to satisfaction

• There are no unnecessary files present in the MR

• The continuous integration has no problems with the MR

• The MR is filled in as requested (including labels, milestones, and reviewers)

• The documentation is up-to-date

• All nullable parameters are marked as such