grpc-timeout header not matching the spec

[tonnyk00]

Hi,

When testing with a deadline in context, the timeout value is converted to nanosecond in grpc-timeout header.
But there is no check of the TimeoutValue range, which could result in the server rejecting the msg with protocol error.

The grpc spec specified that the TimeoutValue can contain at most 8 digits:

TimeoutValue → {positive integer as ASCII string of at most 8 digits}

Best regards,
Tonny

[tsloughter]

Ah thanks!