Initial feature gating and A/B testing integration (#3122)

* Add statsig dependency

* Add SDK provider

* Move to separate file, add tier and hashing

* Disable local storage for now

* Add initial gate testing fixture

* Fork for web just in case

* More WIP

* wip

* Rm test gate

* Add shim on native

* Clarify

src/lib/statsig/statsig.tsx

@@ -0,0 +1,11 @@
+import React from 'react'
+
+export function useGate(_gateName: string) {
+  // Not enabled for native yet.
+  return false
+}
+
+export function Provider({children}: {children: React.ReactNode}) {
+  // Not enabled for native yet.
+  return children
+}

src/lib/statsig/statsig.web.tsx

@@ -0,0 +1,51 @@
+import React from 'react'
+import {StatsigProvider, useGate as useStatsigGate} from 'statsig-react'
+import {useSession} from '../../state/session'
+import {sha256} from 'js-sha256'
+
+const statsigOptions = {
+  environment: {
+    tier: process.env.NODE_ENV === 'development' ? 'development' : 'production',
+  },
+  // Don't block on waiting for network. The fetched config will kick in on next load.
+  // This ensures the UI is always consistent and doesn't update mid-session.
+  // Note this makes cold load (no local storage) and private mode return `false` for all gates.
+  initTimeoutMs: 1,
+}
+
+export function useGate(gateName: string) {
+  const {isLoading, value} = useStatsigGate(gateName)
+  if (isLoading) {
+    // This should not happen because of waitForInitialization={true}.
+    console.error('Did not expected isLoading to ever be true.')
+  }
+  return value
+}
+
+function toStatsigUser(did: string | undefined) {
+  let userID: string | undefined
+  if (did) {
+    userID = sha256(did)
+  }
+  return {userID}
+}
+
+export function Provider({children}: {children: React.ReactNode}) {
+  const {currentAccount} = useSession()
+  const currentStatsigUser = React.useMemo(
+    () => toStatsigUser(currentAccount?.did),
+    [currentAccount?.did],
+  )
+  return (
+    <StatsigProvider
+      sdkKey="client-SXJakO39w9vIhl3D44u8UupyzFl4oZ2qPIkjwcvuPsV"
+      mountKey={currentStatsigUser.userID}
+      user={currentStatsigUser}
+      // This isn't really blocking due to short initTimeoutMs above.
+      // However, it ensures `isLoading` is always `false`.
+      waitForInitialization={true}
+      options={statsigOptions}>
+      {children}
+    </StatsigProvider>
+  )
+}