Lemon Chicken and Spinach Orzo Soup

boneless (, skinless chicken breasts)

Salt and freshly ground black pepper

olive oil (, divided)

chopped carrots ((about 3 large))

chopped celery ((about 3 stalks))

chopped yellow onion ((1 medium))

garlic (, minced)

chicken broth

dried oregano

each dried basil (, dried thyme, and dried rosemary)

dried orzo pasta

parmesan rind (, plus shredded parmesan for serving)

lemon zest

fresh lemon juice

(5 packed cups) fresh spinach, roughly chopped