QES: Mix signature levels across Signers

You can now mix signature levels across Signers in a single Signature Request, including Qualified Electronic Signature (QES). Previously, all Signers had to share the same QES signature level when at least one Signer was at QES level.

You can freely combine SES, AES, and QES Signers in the same Signature Request.
ordered_signers must be set to true on the Signature Request (see Create a Signature Request).

For full details, see the QES level specificities guide and the Set the signature level guide.