fix: ignore empty json strings for locale

[muhlemmer]

This change reverts fbf009f so that any non-value error is returned again.
Instead, a check is done for an empty JSON string.

Extra test cases of missing / null / empty values are also added.

This is an alternative solution for #672

Definition of Ready

• I am happy with the code
• Short description of the feature/issue is added in the pr description
• PR is linked to the corresponding user story
• Acceptance criteria are met
• All open todos and follow ups are defined in a new ticket and justified
• Deviations from the acceptance criteria and design are agreed with the PO and documented.
• No debug or dead code
• My code has no repetitions
• Critical parts are tested automatically
• Where possible E2E tests are implemented
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• All non-functional requirements are met
• Functionality of the acceptance criteria is checked manually on the dev system.

[muhlemmer]

@muir can you have a look if this alternative does not re-introduce the okta issue you had?

[muir]

@muir can you have a look if this alternative does not re-introduce the okta issue you had?

This should be fine. I don't think I would ever want authorization to be blocked by a bad locale though -- I'm not using the locale and thus it has no value.