Fix validation of champva member number

[michaelclement]

The member number validation on the frontend does not match that on the backend. We need to fix this asap as it causes form submissions to fail.

[michaelclement]

The member number on claims is technically supposed to be a social security number, but in the future the team that controls this process is going to switch to using a value that isn't the SSN.

Our problem is that we left the normal SSN validation off this field (because technically in future it may not be an SSN), but the validation we do have is not consistent with what the backend is checking.

The backend validates that we have 8-9 characters (all numbers). We allow more characters than that on the frontend.

[michaelclement]

Work done in this PR. Waiting on:

• [X] Team approval
• [x] Platform approval

[michaelclement]

The above PR ensures that the front-end validation agrees with the backend validation. Whether or not we will change that validation in the future depends on policy decisions (i.e., keep the SSN formatting, use something new that matches whatever the new member structure is - waiting on stakeholder input).

This is meant to keep our current experience from breaking and can be revisited in the future when those decisions have been made.

[michaelclement]

@marywang2 The above fix has been merged. Changes should be visible on staging shortly. Thanks!

[michaelclement]

	screen
Too short
Numbers only
Too long	(users are not able to enter more than 9 digits)

[marywang2]

We will need to revisit error messaging with CAIA but can do in another ticket.