Updating Sharepoint metadata using REST api gives 400 bad request error - rest

Question

I am trying to update a Sharepoint file's metadata using the Indy TidHTTP component in my Delphi program.
Within this program I have successfully managed to do everything else I need to do with the Sharepoint files (create/rename/delete/edit/Checkout etc). But whenever I try to update some metadata property I get a "400 Bad Request" exception.
I know that my RequestDigest string is correct because I am able to upload new contents to the file.
I have seen many similar problems reported and have tried all of the suggestions without success.
(One suggestion was to access the file as a list item rather than using the file url, which I have done in the code below.)
var
str,body,MyUrl: string;
stream: TStringStream;
begin
MyUrl:=MySite+'_api/web/Lists/getByTitle(''CM Library'')/Items(2)';
body:='{"__metadata":{"type":"SP.Data.CM_x0020_LibraryItem"},"Title":"UpdatedTitle"}';
stream := TStringStream.Create(body, TEncoding.UTF8);
try
IdHTTP.Request.Accept:='application/json;odata=verbose';
IdHTTP.Request.ContentType:='application/json';
IdHTTP.Request.ContentLength:=stream.size;
IdHTTP.Request.CustomHeaders.Values['X-RequestDigest']:=RequestDigest;
IdHTTP.Request.CustomHeaders.Values['IF-MATCH']:='*';
IdHTTP.Request.CustomHeaders.Values['X-HTTP-Method']:='MERGE';
try
str := IdHTTP.Post(MyUrl,stream);
except
on E : Exception do
ShowMessage('Exception: '+E.Message);
end;
finally
stream.Free;
end;
// Displays 'Exception: HTTP/1.1 400 Bad Request'

Answer 1

I found it! I needed to add ";odata=verbose" to Request.ContentType (as well as Request.Accept)
Sorry to trouble the community, but I was struggling with this for several days!!