Improve API Request Validations

[betsyecastro]

Implements the following API request validation rules:

• Person (slug): Must contain only alphanumeric characters and periods.
• Search fields: Must be at least three characters long.
• School: Must match one of the whitelisted school short names.
• With data: Allowed only when the person parameter is present.

[shukla-m]

@betsyecastro I added myself as a reviewer on this PR, as we discussed last week, and pulled in the code to test locally. I tried the following URL which passes validation for the person and with_data fields. The person query parameter is invalid - yes I was trying to break it! 😃

http://profiles.test/api/v1?with_data=1&data_type=information&public=1&person=herve;abdi

This might not be an issue but wanted to mention, in case ProfileApiRequest.php@validateWithData() method needed to check for valid person in addition to the existing check for non-empty person. Let me know if you would like to look at it together or discuss. Thanks.

[shukla-m]

Looks good! I tested the updates locally and it seemed to work as expected. See comment regarding person query parameter with invalid value, in case it causes any issues.