Hexadecimal certificate serial number in entity alias metadata would be great

[stormshield-gt]

Is your feature request related to a problem? Please describe.

When using TLS authentication with the metadata of entity aliases activated with enable_identity_alias_metadata, the serial number is returned as a string representation of its decimal value.
For instance "207720964414718439776028734852258731377870138924".

Here is the following code that does that:

vault/builtin/credential/cert/path_login.go

Line 149 in d1e30ba

"serial_number": clientCerts[0].SerialNumber.String(),

This representation is not very convenient to use, because all the endpoints of the PKI API take the hexadecimal representation of the serial number separated with colon.
We can still recreate this representation at the client side, but because the integer is bigger than u128, for most of the programming languages, we must use an external library to parse it. As supply chain attacks are a big concern for me, I would like to have the fewest dependency as possible.

Describe the solution you'd like

Would you be OK to return the hexadecimal representation directly?
I think it's just a matter of calling this function

vault/sdk/helper/certutil/helpers.go

Line 112 in d1e30ba

func GetHexFormatted(buf []byte, sep string) string {

Describe alternatives you've considered

Adding an external library at the client side and build the hexadecimal representation from here.