feat(frontend): remove create brain step in onboarding when share brain (#2791)

# Description

Please include a summary of the changes and the related issue. Please
also include relevant motivation and context.

## Checklist before requesting a review

Please delete options that are not relevant.

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented hard-to-understand areas
- [ ] I have ideally added tests that prove my fix is effective or that
my feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged

## Screenshots (if appropriate):

frontend/app/invitation/[brainId]/hooks/useInvitation.ts

@@ -9,6 +9,7 @@ import { useTranslation } from "react-i18next";
 import { BrainRoleType } from "@/app/studio/[brainId]/BrainManagementTabs/components/PeopleTab/BrainUsers/types";
 import { useSubscriptionApi } from "@/lib/api/subscription/useSubscriptionApi";
 import { useBrainContext } from "@/lib/context/BrainProvider/hooks/useBrainContext";
+import { useOnboardingContext } from "@/lib/context/OnboardingProvider/hooks/useOnboardingContext";
 import { useToast } from "@/lib/hooks";
 import { useEventTracking } from "@/services/analytics/june/useEventTracking";
 
@@ -21,6 +22,7 @@ export const useInvitation = () => {
   const [brainName, setBrainName] = useState<string>("");
   const [role, setRole] = useState<BrainRoleType | undefined>();
   const [isProcessingRequest, setIsProcessingRequest] = useState(false);
+  const { setIsBrainCreated } = useOnboardingContext();
 
   const { publish } = useToast();
   const { track } = useEventTracking();
@@ -63,6 +65,7 @@ export const useInvitation = () => {
   }, [brainId]);
 
   const handleAccept = async () => {
+    setIsBrainCreated(true);
     setIsProcessingRequest(true);
     try {
       await acceptInvitation(brainId);

frontend/lib/components/OnboardingModal/OnboardingModal.tsx

@@ -14,8 +14,11 @@ import { SingleSelector } from "../ui/SingleSelector/SingleSelector";
 import { TextInput } from "../ui/TextInput/TextInput";
 
 export const OnboardingModal = (): JSX.Element => {
-  const { isOnboardingModalOpened, setIsOnboardingModalOpened } =
-    useOnboardingContext();
+  const {
+    isOnboardingModalOpened,
+    setIsOnboardingModalOpened,
+    isBrainCreated,
+  } = useOnboardingContext();
 
   const methods = useForm<OnboardingProps>({
     defaultValues: {
@@ -46,7 +49,7 @@ export const OnboardingModal = (): JSX.Element => {
     await updateUserIdentity({
       username: methods.getValues("username"),
       company: methods.getValues("companyName"),
-      onboarded: false,
+      onboarded: isBrainCreated,
       company_size: methods.getValues("companySize"),
       usage_purpose: methods.getValues("usagePurpose") as
         | UsagePurpose