feat: Use FirstOrDefaultAsync for contract retrieval#209

kamilbaczek merged 3 commits intomainevolutionary-architecture/evolutionary-architecture-by-example:mainfrom

208-use-of-singleordefaultasync-may-throw-exception-when-multiple-contracts-exist-for-the-same-customerevolutionary-architecture/evolutionary-architecture-by-example:208-use-of-singleordefaultasync-may-throw-exception-when-multiple-contracts-exist-for-the-same-customerCopy head branch name to clipboard