Block rewards API endpoint (#12020)

Co-authored-by: terencechain <terence@prysmaticlabs.com>
Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>

api/gateway/gateway.go

@@ -70,15 +70,16 @@ type Gateway struct {
 func New(ctx context.Context, opts ...Option) (*Gateway, error) {
 	g := &Gateway{
 		ctx: ctx,
-		cfg: &config{
-			router: mux.NewRouter(),
-		},
+		cfg: &config{},
 	}
 	for _, opt := range opts {
 		if err := opt(g); err != nil {
 			return nil, err
 		}
 	}
+	if g.cfg.router == nil {
+		g.cfg.router = mux.NewRouter()
+	}
 	return g, nil
 }
 

api/gateway/options.go

@@ -10,11 +10,6 @@ import (
 
 type Option func(g *Gateway) error
 
-func (g *Gateway) SetRouter(r *mux.Router) *Gateway {
-	g.cfg.router = r
-	return g
-}
-
 func WithPbHandlers(handlers []*PbMux) Option {
 	return func(g *Gateway) error {
 		g.cfg.pbHandlers = handlers