fix duration months 30 days

[prunelsigma]

fix the asset frequency/ range to allow month duration to be next month same day instead of 30 days
examples:
currently P1MT => each 30 days
allow to be P1MT => next month of StartDate

info :

• https://github.com/cryptogarageinc/p2pderivatives-oracle/blob/2aa200c316cdbe2b7f8aa9388479e69f11133a90/internal/utils/iso8601/duration.go#L17
• https://github.com/cryptogarageinc/p2pderivatives-oracle/blob/develop/internal/api/api_config.go