The type of PSA elliptic curve family identifiers. Values of this type are generally constructed by macros called `PSA_ECC_FAMILY_xxx`. The curve identifier is required to create an ECC key using the PSA_KEY_TYPE_ECC_KEY_PAIR() or PSA_KEY_TYPE_ECC_PUBLIC_KEY() macros. Values defined by this standard will never be in the range 0x80-0xff. Vendors who define additional families must use an encoding in this range.