Creates a list to hold GWAS Catalog metadata.
metadata_lst(
ensembl_release_number = NA_integer_,
genome_build_version = NA_character_,
dbsnp_version = NA_integer_,
usage_start_date = lubridate::ymd_hms()
)A list of 4 named elements as passed as arguments:
ensembl_release_number, genome_build_version,
dbsnp_version and usage_start_date.
Date since this combination of resource versions has been in use.