Adding invoice UUID to PayReq and PayReqResponse, for uma invoice

[matthappens]

Add UMA invoice id to PayRequest

for PayRequest V1, add a uuid reference to uma invoice

reference: uma-universal-money-address/uma-go-sdk@79965e4

[matthappens]

• Adding invoice UUID to PayReq and PayReqResponse, for uma invoice #58 👈
• main

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[zhenlu]

invoice uuid included in the metadata json