Make free coaching call url configurable and popup translatable (#823)

app/common/gristUrls.ts

@@ -675,6 +675,9 @@ export interface GristLoadConfig {
   // Url for support for the browser client to use.
   helpCenterUrl?: string;
 
+  // Url for free coaching call scheduling for the browser client to use.
+  freeCoachingCallUrl?: string;
+
   // When set, this directs the client to encode org information in path, not in domain.
   pathOnly?: boolean;
 
@@ -879,6 +882,15 @@ export function getHelpCenterUrl(): string|null {
   }
 }
 
+export function getFreeCoachingCallUrl(): string|null {
+  if(isClient()) {
+    const gristConfig: GristLoadConfig = (window as any).gristConfig;
+    return gristConfig && gristConfig.freeCoachingCallUrl || null;
+  } else {
+    return process.env.FREE_COACHING_CALL_URL || null;
+  }
+}
+
 /**
  * Like getKnownOrg, but respects singleOrg/GRIST_SINGLE_ORG strictly.
  * The main difference in behavior would be for orgs with custom domains