[#562] Support TLS termination header for SSE-C

The TLS termination header added for determining
whether TLS needs to be checked. If the system
requests come through a proxy server and TLS can
terminate at the proxy level, you should use this
header to disable TLS verification at SSE-C.

Signed-off-by: Roman Loginov <r.loginov@yadro.com>

api/handler/api.go

@@ -41,6 +41,7 @@ type (
 		RetryMaxAttempts() int
 		RetryMaxBackoff() time.Duration
 		RetryStrategy() RetryStrategy
+		TLSTerminationHeader() string
 	}
 
 	FrostFSID interface {