Return error for bad content-type
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Check content type along with content length
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)
Merge pull request #7385 from crosbymichael/return-content-type-error

Return error for bad content-type
Accept vanilla Linux Foundation signoffs

This allows signing off commits with `git commit -s`

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

Cleaned up DCO regex
Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)
Update CONTRIBUTING.md and test new DCO signature in this commit

Signed-off-by: Tibor Vass <teabee89@gmail.com>