chore: Add PAYG trial events flag to Unleash (#10336)

Pretty much what it says on the tin: add PAYG trial events flag to
control the upcoming trial events

src/lib/types/experimental.ts

@@ -63,6 +63,7 @@ export type IFlagKey =
     | 'improvedJsonDiff'
     | 'crDiffView'
     | 'changeRequestApproverEmails'
+    | 'paygTrialEvents'
     | 'eventGrouping';
 
 export type IFlags = Partial<{ [key in IFlagKey]: boolean | Variant }>;
@@ -296,6 +297,10 @@ const flags: IFlags = {
         process.env.UNLEASH_EXPERIMENTAL_EVENT_GROUPING,
         false,
     ),
+    paygTrialEvents: parseEnvVarBoolean(
+        process.env.UNLEASH_EXPERIMENTAL_PAYG_TRIAL_EVENTS,
+        false,
+    ),
 };
 
 export const defaultExperimentalOptions: IExperimentalOptions = {

src/server-dev.ts

@@ -58,6 +58,7 @@ process.nextTick(async () => {
                         impactMetrics: true,
                         crDiffView: true,
                         eventGrouping: true,
+                        paygTrialEvents: true,
                     },
                 },
                 authentication: {