Fix/vaultaddr response parsing

[terwey]

Pull Request

Description

Fixes multiple issues in API response handling and request building:

• Correctly parse response.data as JSON when it’s an object or array.
• Omit vaultAddress from payloads when empty to avoid API 422 errors.
• Change OrderStatus.Error from *error to *string for proper unmarshalling, and add a String() helper for easier debugging.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Performance improvement

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have run make ci-full and all checks pass

The existing tests pass/fail the same as before, they are broken. Not going to fix them.

Code Quality

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

[coveralls]

Pull Request Test Coverage Report for Build 16852915467

Details

• 0 of 20 (0.0%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.04%) to 11.892%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
exchange_orders.go	0	3	0.0%
api.go	0	6	0.0%
exchange.go	0	11	0.0%

Files with Coverage Reduction	New Missed Lines	%
exchange_orders.go	1	0.0%

Totals
Change from base Build 16777118411:	-0.04%
Covered Lines:	325
Relevant Lines:	2733

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💛 - Coveralls

[sonirico]

thx! @terwey