Enforce Go style rules across codebase

Apply five style rules: convert iota string enums to typed
string constants, replace errors.As with errors.AsType,
merge three-group imports into two groups, fix multiline
parameter/argument formatting, and replace fmt.Sprintf URL
construction with net/url.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/server/gqlutils/handler.go

@@ -22,7 +22,6 @@ import (
 	"github.com/99designs/gqlgen/graphql/handler"
 	"github.com/99designs/gqlgen/graphql/handler/extension"
 	"github.com/99designs/gqlgen/graphql/handler/transport"
-
 	"go.gearno.de/kit/log"
 )