fix : Incorrect date formatting and masked error messages

[DivyanshuVortex]

Summary

This PR fixes a bug in date calculation and improves how the library reports errors.

Why this is important

• Fixes Broken Logic: Corrects a bug where querying service usage for a specific date returned wrong results because the month was calculated incorrectly.
• Better Developer Experience: Instead of crashing with a generic "JSON error," the library now shows the actual reason for a failure (e.g., "File not found"), making it much easier to debug.
• Test Integrity: Added new tests to guarantee that date-based verification works perfectly and won't break in the future.

Changes

• Fixed formatDate month indexing and padding.
• Surfaced real error messages from the Microcks API.
• Fixed typos in error strings.
• Added regression tests for date verification.

Fixes : #202