* Trim whitespace from tokens before logging in

This change trims whitespace characters from the supplied token before it is used to log in. Users can encounter this accidentally if they read their token from a file that ends with a blank line.

Leading whitespace will make the token invalid. Trailing whitespace or \n (not \r\n) will also fail to log in. \r\n (CRLF) doesn't fail because of the line break style for http request headers.

* revert trimming api token

* add check for whitespace or newline characters to existing token validation

Checks to see if a token contains any illegal characters, like whitespace or a newline. If it is, throws an ArgumentException warning the user that their token may be invalid.

I considered only checking the first and last character, but given that a token containing whitespace or a newline wouldn't work either I figured this made sense.

* removed unused usings

These were leftover from a previous approach using an ImmutableHashSet