Refactor: use DspNamespace instead of hardcoded Strings

[wolf4ood]

Feature Request

The DspNamespace was introduces in #4557 which represent a namespace to use for a protocol version.

We should refactor the DSP validators and transformers to use DspNamespace instead of Strings

Which Areas Would Be Affected?

e.g., DPF, CI, build, transfer, etc.

Why Is the Feature Desired?

Are there any requirements?

Solution Proposal

If possible, provide a (brief!) solution proposal.