Add is-subset and is-subset-ci operator modes for list comparison

[michalis1]

Issue #149

This PR introduces two new operator modes to jdiff:

• is-subset
• is-subset-ci

These operators allow validation of list-valued fields by checking whether the extracted list is a subset of a reference list. jdiff currently supports scalar comparisons but does not provide a built-in mechanism to validate that an extracted list is contained within an allowed set. This PR adds subset comparison operators to address that use case.

• is-subset: Validates that the extracted list is a subset of the reference list
• is-subset-ci: Same as is-subset but case-insensitive

Example:

check_args = {
    "params": {
        "mode": "is-subset",
        "operator_data": allowed_domains
    }
}

Enhancement to associate_key_of_my_value()

A small improvement was required to support extraction paths where a single selected field contains a list value [*].[$id$,include_trusted_domains]. Previously, such cases raised ValueError("Key's value len != from value len") because the function interpreted list elements as separate field values. This required a small enhancement in associate_key_of_my_value() to correctly interpret cases where a single extracted field contains a list value instead of treating the list elements as separate field values.

Example JSON:

[
  {
    "id": "DOMAIN1.COMPANY.COM",
    "include_trusted_domains": [
      "COMPANY.COM",
      "domain1.company.com",
      "domain2.company.COM",
      "domain3.company.com",
      "test.com"
    ]
  }
]