Create async wrapper on FC API client

[mats-stripe]

Summary

Motivation

Testing

Changelog

[github-actions]

🚨 New dead code detected in this PR:

FinancialConnectionsAsyncAPIClient.swift:19 warning: Protocol 'FinancialConnectionsAsyncAPI' is redundant as it's never used as an existential type
FinancialConnectionsAsyncAPIClient.swift:191 warning: Protocol 'FinancialConnectionsAsyncAPI' conformance is redundant
FinancialConnectionsAsyncAPIClient.swift:192 warning: Function 'synchronize(clientSecret:returnURL:)' is unused
FinancialConnectionsAsyncAPIClient.swift:211 warning: Function 'fetchFinancialConnectionsAccounts(clientSecret:startingAfterAccountId:)' is unused
FinancialConnectionsAsyncAPIClient.swift:230 warning: Function 'fetchFinancialConnectionsSession(clientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:264 warning: Function 'fetchFeaturedInstitutions(clientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:281 warning: Function 'fetchInstitutions(clientSecret:query:)' is unused
FinancialConnectionsAsyncAPIClient.swift:300 warning: Function 'createAuthSession(clientSecret:institutionId:)' is unused
FinancialConnectionsAsyncAPIClient.swift:319 warning: Function 'cancelAuthSession(clientSecret:authSessionId:)' is unused
FinancialConnectionsAsyncAPIClient.swift:338 warning: Function 'retrieveAuthSession(clientSecret:authSessionId:)' is unused
FinancialConnectionsAsyncAPIClient.swift:357 warning: Function 'fetchAuthSessionOAuthResults(clientSecret:authSessionId:)' is unused
FinancialConnectionsAsyncAPIClient.swift:376 warning: Function 'authorizeAuthSession(clientSecret:authSessionId:publicToken:)' is unused
FinancialConnectionsAsyncAPIClient.swift:397 warning: Function 'fetchAuthSessionAccounts(clientSecret:authSessionId:initialPollDelay:)' is unused
FinancialConnectionsAsyncAPIClient.swift:418 warning: Function 'selectAuthSessionAccounts(clientSecret:authSessionId:selectedAccountIds:)' is unused
FinancialConnectionsAsyncAPIClient.swift:439 warning: Function 'markLinkingMoreAccounts(clientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:456 warning: Function 'completeFinancialConnectionsSession(clientSecret:terminalError:)' is unused
FinancialConnectionsAsyncAPIClient.swift:475 warning: Function 'attachBankAccountToLinkAccountSession(clientSecret:accountNumber:routingNumber:consumerSessionClientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:498 warning: Function 'attachLinkedAccountIdToLinkAccountSession(clientSecret:linkedAccountId:consumerSessionClientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:519 warning: Function 'recordAuthSessionEvent(clientSecret:authSessionId:eventNamespace:eventName:)' is unused
FinancialConnectionsAsyncAPIClient.swift:542 warning: Function 'saveAccountsToNetworkAndLink(shouldPollAccounts:selectedAccounts:emailAddress:phoneNumber:country:consumerSessionClientSecret:clientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:574 warning: Function 'disableNetworking(disabledReason:clientSuggestedNextPaneOnDisableNetworking:clientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:595 warning: Function 'fetchNetworkedAccounts(clientSecret:consumerSessionClientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:614 warning: Function 'selectNetworkedAccounts(selectedAccountIds:clientSecret:consumerSessionClientSecret:consentAcquired:)' is unused
FinancialConnectionsAsyncAPIClient.swift:637 warning: Function 'markLinkStepUpAuthenticationVerified(clientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:654 warning: Function 'consumerSessionLookup(emailAddress:clientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:673 warning: Function 'consumerSessionStartVerification(otpType:customEmailType:connectionsMerchantName:consumerSessionClientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:696 warning: Function 'consumerSessionConfirmVerification(otpCode:otpType:consumerSessionClientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:717 warning: Function 'markLinkVerified(clientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:734 warning: Function 'linkAccountSignUp(emailAddress:phoneNumber:country:amount:currency:incentiveEligibilitySession:)' is unused
FinancialConnectionsAsyncAPIClient.swift:761 warning: Function 'attachLinkConsumerToLinkAccountSession(linkAccountSession:consumerSessionClientSecret:)' is unused
FinancialConnectionsAsyncAPIClient.swift:780 warning: Function 'paymentDetails(consumerSessionClientSecret:bankAccountId:billingAddress:billingEmail:)' is unused
FinancialConnectionsAsyncAPIClient.swift:803 warning: Function 'sharePaymentDetails(consumerSessionClientSecret:paymentDetailsId:expectedPaymentMethodType:billingEmail:billingPhone:)' is unused
FinancialConnectionsAsyncAPIClient.swift:828 warning: Function 'paymentMethods(consumerSessionClientSecret:paymentDetailsId:billingDetails:)' is unused
ConsentDataSource.swift:9 warning: Imported module 'StripeCore' is unused
ConsentViewController.swift:10 warning: Imported module 'StripeCore' is unused

Please remove the dead code before merging.

If this is intentional, you can bypass this check by adding the label skip dead code check to this PR.

ℹ️ If this comment appears to be left in error, double check that the flagged code is actually used and/or make sure your branch is up-to-date with master.