Switch device structure to optional

[bigludo7]

What type of PR is this?

Add one of the following kinds:

• enhancement/feature

What this PR does / why we need it:

Shift device structure cardinality to optional has the device identifier could be obtained from the 3-legs process.

Which issue(s) this PR fixes:

Fixes #173

Special notes for reviewers:

Changelog input

 release-note
- Device structure is now optional has the device identifier could be obtained from the 3-legs process.

Additional documentation

This section can be blank.

docs

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ ACTION	actionlint	2		0	0.03s
✅ OPENAPI	spectral	5		0	7.77s
✅ REPOSITORY	git_diff	yes		no	0.01s
✅ REPOSITORY	secretlint	yes		no	0.83s
✅ YAML	yamllint	5		0	0.84s

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[bigludo7]

@sachinvodafone @akoshunyadi @fernandopradocabrillo Gentle reminder for this one as is it a simple one.
As we're close to the finish line and there is few other topic to adress for these API like error code.
Thanks