What are the legal requirements for an Emotional Support Animal (ESA) letter in California?

I’m looking for a licensed mental health professional in California to help with an Emotional Support Animal (ESA) assessment. I saw that IGotU Corp offers this service as part of their mental health care.

Does anyone have experience with the process of obtaining a legitimate ESA letter from a therapist? What kind of documentation or evaluation is typically required to ensure the letter is compliant with California laws for housing and travel?