PUT doesn't set a proper mimetype

[ryanmcgrath]

I might be missing something, but calls to putObjectWithFile don't actually set a mimetype anywhere before the AWS signature is generated. This results in the uploaded file having the incorrect mimetype when it's uploaded (so a browser, for instance, downloads it rather than displaying it if it can). If you change the mimetype after the signature has been generated your upload will be rejected due to a signature mismatch.

My (hacky) fix was to add the following...

    if([request.HTTPMethod compare:@"PUT" options:NSCaseInsensitiveSearch] == NSOrderedSame) {
        for(NSString *keyPath in parameters) {
            [request setValue:parameters[keyPath] forHTTPHeaderField:keyPath];
        }
    }

in AFAmazonS3RequestSerializer.m's requestWithMethod:URLString:parameters:error method:

- (NSMutableURLRequest *)requestWithMethod:(NSString *)method
                                 URLString:(NSString *)URLString
                                parameters:(NSDictionary *)parameters
                                     error:(NSError *__autoreleasing *)error

After that, I modified AFAmazonS3Manager.m and changed

        request = [self.requestSerializer requestWithMethod:method URLString:[[self.baseURL URLByAppendingPathComponent:destinationPath] absoluteString] parameters:nil error:nil];

to

        request = [self.requestSerializer 
            requestWithMethod:method 
                           URLString:[[self.baseURL URLByAppendingPathComponent:destinationPath] absoluteString] 
                         parameters:@{@"Content-Type": [response MIMEType]} 
                                    error:nil];

The mimetype is already being computed for the POST method but never gets properly set for a PUT. This annoyed me for a bit so I'm leaving it here - I don't have the time to do a proper pull request/test/etc, so maybe this helps someone else. Dealing with the official AWS libraries is a PITA in my experience so it'd be nice if this was kept up to date...