Add flag to send email signups to staging instead of prod (#196)

## Description

This is a no-op for the moment; Zuplo-side change to read the flag and
act on it is upcoming.

## Test Plan

Watch network traffic in web inspector.

With the flag set, submit an email and make sure the flag is present
and set to true in the payload.

Without the flag set, submit an email and make sure the flag is not
in the payload at all.

src/email-signup.ts

@@ -18,6 +18,7 @@ export async function submitEmailSignup(
   apiKey: string,
   formValues: FormValues,
   emailRequired: boolean,
+  emailToStaging: boolean,
 ): Promise<boolean> {
   safeLocalStorage.setItem(LOCAL_STORAGE_KEY, true);
 
@@ -27,7 +28,12 @@ export async function submitEmailSignup(
 
     const response = await fetch(url, {
       method: 'POST',
-      body: JSON.stringify({ ...formValues, emailRequired }),
+      body: JSON.stringify({
+        ...formValues,
+        emailRequired,
+        // Only include this if it's true
+        emailToStaging: emailToStaging ? true : undefined,
+      }),
       headers: {
         Authorization: `Bearer ${apiKey}`,
         'Content-Type': 'application/json',

src/state-calculator.tsx

@@ -114,6 +114,7 @@ const StateCalculator: FC<{
   stateId?: string;
   showEmail: boolean;
   emailRequired: boolean;
+  emailToStaging: boolean;
   includeBetaStates: boolean;
 }> = ({
   shadowRoot,
@@ -123,6 +124,7 @@ const StateCalculator: FC<{
   stateId,
   showEmail,
   emailRequired,
+  emailToStaging,
   includeBetaStates,
 }) => {
   const { msg, locale } = useTranslated();
@@ -171,7 +173,13 @@ const StateCalculator: FC<{
     safeLocalStorage.setItem(FORM_VALUES_LOCAL_STORAGE_KEY, formValues);
 
     if (formValues.email && !emailSubmitted) {
-      submitEmailSignup(apiHost, apiKey, formValues, emailRequired);
+      submitEmailSignup(
+        apiHost,
+        apiKey,
+        formValues,
+        emailRequired,
+        emailToStaging,
+      );
       // This hides the email field
       setEmailSubmitted(true);
     }
@@ -282,6 +290,12 @@ class CalculatorElement extends HTMLElement {
    */
   emailRequired: boolean = false;
 
+  /**
+   * Property to submit emails to the staging environment instead of prod.
+   * Intentionally undocumented; for RA use only.
+   */
+  emailToStaging: boolean = false;
+
   /* property to include incentives from states that aren't formally launched */
   includeBetaStates: boolean = false;
 
@@ -304,6 +318,7 @@ class CalculatorElement extends HTMLElement {
     'lang',
     'show-email',
     'email-required',
+    'email-to-staging',
     'include-beta-states',
     'api-key',
     'api-host',
@@ -358,6 +373,8 @@ class CalculatorElement extends HTMLElement {
       this.showEmail = newValue !== null;
     } else if (attr === 'email-required') {
       this.emailRequired = newValue !== null;
+    } else if (attr === 'email-to-staging') {
+      this.emailToStaging = newValue !== null;
     } else if (attr === 'state') {
       this.state = newValue ?? '';
     } else if (attr === 'zip') {
@@ -398,6 +415,7 @@ class CalculatorElement extends HTMLElement {
           stateId={this.state}
           showEmail={this.showEmail}
           emailRequired={this.emailRequired}
+          emailToStaging={this.emailToStaging}
           includeBetaStates={this.includeBetaStates}
         />
       </LocaleContext.Provider>,