Externalize service API yaml contracts

account-management/pom.xml

account-query/pom.xml

m2m-banking-api/README.md

m2m-banking-api/account-management-api/openapi.yaml

m2m-banking-api/account-management-api/pom.xml

m2m-banking-api/account-query-api/openapi.yaml

m2m-banking-api/account-query-api/pom.xml

m2m-banking-api/pom.xml

m2m-banking-api/transaction-api/openapi.yaml

m2m-banking-api/transaction-api/pom.xml

transaction-processor/pom.xml