Check schema_input.json

[FernandoDuarteF]

Check 'required' field in schema_input.json, as right now only the 'species' field is mandatory in the samplesheet for input schema validation.

The reason why only 'species' is required right now is that input samplesheet is flexible, meaning it can accept samples with different field information -e.g., a sample can have a RefSeq ID while another sample can have local files.

[FernandoDuarteF]

To solve this we first nee to migrate to nf-schema.