SDK users sbat request a variable number of attestations at once, with a default of 3

[nityas]

Expected Behavior

per https://github.com/celo-org/celo-labs/issues/80#issuecomment-541174310, we give a caller flexibility to request variable #s of attestations at any point in time, with the ability to

• Make the default number of attestations requested 3 (optional param with default?), add some documentation explaining the reason for this default and the implications of using a number less than 3.
• add a function that allows a caller to easily determine if a verified phone number had >= 3 attestations requested at once, or if they were requested spaced out over a long period of time

Current Behavior

What is the current behavior?

[github-actions]

This issue is stale and will be closed in 30 days without activity