SPDX 2.3: LicenseRefs should not be case insensitive

According to the spec license expressions case sensitivity section, SPDX license IDs should be treated as case insensitive while LicenseRef's should be considered case sensitive.

Currently, if 2 license refs are found that differ only in case, an error is generated.

This situation should be allowed.

For example:

{
      "licenseId": "LicenseRef-BSD-3-clause-GENERIC",
      "extractedText": "NOASSERTION",
      "name": "BSD-3-clause-GENERIC"
    },
[...]
    {
      "licenseId": "LicenseRef-BSD-3-clause-generic",
      "extractedText": "NOASSERTION",
      "name": "BSD-3-clause-generic"
    },

should be allowed.

The error generated is Analysis exception processing SPDX file: Object URI ...#LicenseRef-BSD-3-clause-generic already exists.

El issue no menciona ningún archivo fuente ni ninguna prueba. Empieza por localizar el código que informa de URI de Object duplicadas para LicenseRefs y las pruebas de análisis existentes; reproduce el caso con dos refs que solo difieran en mayúsculas y minúsculas, y confirma después que ambas se aceptan, mientras que los IDs de licencia SPDX siguen gestionándose sin distinguir mayúsculas y minúsculas.