fix : multipleOf only considers case that fail in allOf

[srivastava-diya]

The issue

Currently, the multipleOf error handler only considers constraints that failed.

If a schema has many multipleOf constraints (e.g in an allOf), such as:

{
  "allOf": [
    { "multipleOf": 2 },
    { "multipleOf": 3 }
  ]
}

instance = 9  //multiple of 3 only

then,

• multipleOf: 3 PASSES.
• multipleOf: 2 FAILS.
• The reported error is: "Expected a number that is a multiple of 2".

Expected behaviour

since both are required, the user effectively requires a multiple of 6. The error message should reflect the combined constraint, even if one of the individual checks passed.

The Fix

This PR updates multipleOf error-handler to:

• Iterate over all multipleOf constraints for the given location, regardless of whether they passed or failed.
• Calculate the LCM of all these constraints.
• Report an error with the combined LCM value if at least one of the constraints failed.

Verification

Test case has been added to cover this.

[jdesrosiers]

Good catch! We found that issue in #155, but it didn't occur to me that this could have the same weakness.