Add missing VC-DI/LD-Proof verification method option

[PatStLouis]

I replaced the custom IssuanceOptionsSchema schema on the vc/issue endpoint with the previous LDProofOptionsSchema. The idea will be to revisit the idea of having custom options field for different endpoints in a post 1.0 version. The verificationMethod option is necessary when issuing using unconventional did methods, such as did:web where the wallet can't correlate a verificationMethod with a specific did

[sonarqubecloud]

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[PatStLouis]

@dbluhm @jamshale this should be a fairly straight forward review. For a refresher, on the vc-api issuance endpoints, if the controller doesn't provide a proofType, it will default to Ed25519Signature2020 or BbsBlsSignature2020 depending on the key method of the did.