Nate, I do a lot of HR-related work, and this response comes from that.
The hiring employer should NOT ask about any medical conditions until after you have agreed to employment - these should NOT appear on the employment application. It is not legal for them to request this information in advance of offer acceptance. It should be included on your ADA (Americans with Disabilities Act) form. In fact, anything that may require "reasonable accommodation" should be put there, along with the type of accommodations you are requesting. You should also update your ADA form if you develop a new condition following initial employment.
You should note, though, that "reasonable accommodation" can mean different things for different employers, and even for different jobs at the same employer. For example, if your job does not really require you to be at a desk from 8-5, and you can reasonably perform your job from your house during "off hours" without creating a negative impact for the employer or their business, then letting you work from home in the evenings when you have a migraine during the say is not an unreasonable request. On the other hand, if the job really requires you to be somewhere during specific times of the day (like possibly a sales clerk at a shoe store who needs to be selling shoes during business hours at the store), then asking to work from home during off hours is not reasonable.
It may be helpful if you spend some time thinking now about how you could perform the job if you had a migraine for an extended period. Could you still work if some sort of accommodations are made? What kinds of accommodations might be "reasonable" for the job? Note you have to look at "reasonable accommodations" from the employer's perspective, not your own. If you can come up with an approach or two that would likely work for the employer, put them on the ADA form as accommodations you are requesting. But note, it's not reasonable to expect the employer to simply allow you not to work on a regular basis - even the courts recognize that your job exists for the benefit of the employer's business, and that most employers cannot "carry" an employee who is simply absent.