Add parsing handler for Subject Directory Attributes #392
Description
FR for x509ext to support a parsing handler if the subject directory attribute is set.
It seems it can hold arbitrary data so this FR is initially to accomodate the TPM Specification component.
from pg 25 : https://trustedcomputinggroup.org/wp-content/uploads/TCG_IWG_Credential_Profile_EK_V2.1_R13.pdf
3.2.11 Subject Directory Attributes
The extension includes miscellaneous properties and security assertions about the entity. This
extension MUST be non-critical.
The following attribute MAY be included in a subject directory attributes extension in the EK
certificate:
* The “TPM Specification” attribute that identifies the family, level and revision of the TCG
TPM specification to which the TPM was designed. The ASN.1 encoding is specified in
section 3.1.3 TPM Specification Attributes.
If the subject directory can contain arbitrary data, maybe an enhancement is for the caller to supply a type struct to unmarshall to