refactor(server): drop the gateway context accessor IdentityFrom replaced

The route wrapper was the only caller, and it now reads the whole identity at once. An exported
accessor nothing reaches is a shape the next handler copies for no reason.

Author: otavio

server/api/pkg/gateway/context.go

@@ -120,12 +120,6 @@ func (c *Context) DeviceUID() string {
 	return c.Request().Header.Get("X-Device-UID")
 }
 
-// APIKey returns the API key the request authenticated with, got from gateway. It is empty when
-// the request was not authenticated with an API key.
-func (c *Context) APIKey() string {
-	return c.Request().Header.Get("X-API-Key")
-}
-
 // Username returns the username got from JWT through gateway.
 func (c *Context) Username() *models.Username {
 	username := c.Request().Header.Get("X-Username")