Merchant Upgrade flow Step 2: add userUpgradeMerchant function

[islandbitcoin]

• Check for rate limit on supabase
• pull test transaction amount for user
• check user entry against test transaction amount
• increment rate limit counter if false
• update user upgrade status if true.

[brh28]

Add graphql mutation (checkTestTransaction) which looks up a test transaction in supabase by the user's phone number and checks the amount of the transaction.

Needs:

• Supabase URL
• Supabase API key

Need to lookup supabase query

[brh28]

Relates to Account upgrade on flash-mobile: https://github.com/lnflash/flash-mobile/pull/400/files

[brh28]