Steamed Mussels in Cherry Tomato Broth

Name: Steamed Mussels in Cherry Tomato Broth
Ingredients: 1 tbsp olive oil; 2 leeks (white parts only thinly sliced); 2 cups cherry tomatoes (halved); 4 garlic cloves (minced); 2 cups vegetable broth; 1 tsp red pepper flakes; 1/2 tsp kosher salt; 1/4 tsp black pepper; 2 tbsp fresh parsley (chopped); 1/2 lemon (juiced); 4 lb mussels; thinly sliced green onion; lemon wedges