/// <summary>
/// get (the) touchpoint id from (the) Postcode
/// </summary>
/// <param name="theCandidate">the candidate</param>
/// <param name="usingScope">using (the logging) scope</param>
/// <returns>the LAD code</returns>
public async Task <string> GetTouchpointIDFromPostcode(string theCandidate, IScopeLoggingContext usingScope)
{
await usingScope.EnterMethod();
await usingScope.Information($"seeking postcode '{theCandidate}'");
var result = await Postcode.LookupAsync(theCandidate);
It.IsNull(result)
.AsGuard <InvalidPostcodeException>(theCandidate);
It.IsEmpty(result.Postcode)
.AsGuard <InvalidPostcodeException>(theCandidate);
await usingScope.Information($"found postcode for '{result.Postcode}'");
await usingScope.Information($"seeking local authority '{result.Codes.AdminDistrict}'");
var authority = await Authority.Get(result.Codes.AdminDistrict);
await usingScope.Information($"found local authority '{authority.LADCode}'");
await usingScope.ExitMethod();
return(authority.TouchpointID);
}