Unicode character can't set in headers! #653

What type of issue are you creating?

• [ x] Bug
• Enhancement
• Question

What version of this module are you using?

• [ x] 2.0.10 (Stable)
• 2.1.0-rc.n (2.1 Release Candidate n)
• Other

I using unicode character to find (filter and where) and get message:
"Cannot convert string to ByteString because the character at index "

In headers, i can't set unicode character without base64 encode.

Please allow change this setting via LoopbackConfig

Please add a description for your issue: