fix(studio): bump realtime max_concurrent_users soft limit (#50438)

## I have read the
[CONTRIBUTING.md](https://github.com/supabase/supabase/blob/master/CONTRIBUTING.md)
file.

YES

## What kind of change does this PR introduce?

Bump realtime max_concurrent_users soft limit to 300k

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Increased the maximum supported concurrent clients from 50,000 to
300,000 when plan entitlements allow it.

* **Bug Fixes**
* Improved validation for concurrent-client limits, including clearer
handling of entitlement-based and unlimited limits.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: Joshen Lim <joshenlimek@gmail.com>

apps/studio/components/interfaces/Realtime/RealtimeSettings.test.tsx

@@ -68,19 +68,28 @@ const REALTIME_CONFIG = {
   suspend: false,
 } as const satisfies RealtimeConfigurationData
 
-const REALTIME_ENTITLEMENTS: Entitlement[] = (
-  [
-    ['realtime.max_concurrent_users', 50_000],
-    ['realtime.max_events_per_second', 50_000],
-    ['realtime.max_presence_events_per_second', 5_000],
-    ['realtime.max_payload_size_in_kb', 3_000],
-  ] satisfies [FeatureKey, number][]
-).map(([key, value]) => ({
-  config: { enabled: true, unit: '', unlimited: false, value },
-  feature: { key, type: 'numeric' },
-  hasAccess: true,
-  type: 'numeric',
-}))
+const buildRealtimeEntitlements = (
+  overrides: Partial<Record<FeatureKey, number | 'unlimited'>> = {}
+): Entitlement[] =>
+  (
+    [
+      ['realtime.max_concurrent_users', 50_000],
+      ['realtime.max_events_per_second', 50_000],
+      ['realtime.max_presence_events_per_second', 5_000],
+      ['realtime.max_payload_size_in_kb', 3_000],
+    ] satisfies [FeatureKey, number][]
+  ).map(([key, value]) => {
+    const override = overrides[key]
+    const unlimited = override === 'unlimited'
+    return {
+      config: { enabled: true, unit: '', unlimited, value: unlimited ? 0 : (override ?? value) },
+      feature: { key, type: 'numeric' },
+      hasAccess: true,
+      type: 'numeric',
+    }
+  })
+
+const REALTIME_ENTITLEMENTS: Entitlement[] = buildRealtimeEntitlements()
 
 describe('RealtimeSettings', () => {
   beforeEach(() => {
@@ -199,4 +208,65 @@ describe('RealtimeSettings', () => {
       expect(requests).toHaveLength(0)
     }
   })
+
+  test.each([
+    { value: '300000', accepted: true },
+    { value: '300001', accepted: false },
+  ])(
+    '$accepted for max concurrent clients of $value when the entitlement is unlimited',
+    async ({ value, accepted }) => {
+      addAPIMock({
+        method: 'get',
+        path: '/platform/organizations/:slug/entitlements',
+        response: {
+          entitlements: buildRealtimeEntitlements({ 'realtime.max_concurrent_users': 'unlimited' }),
+        },
+      })
+
+      const requests: unknown[] = []
+      addAPIMock({
+        method: 'patch',
+        path: '/platform/projects/:ref/config/realtime',
+        response: async ({ request }) => {
+          requests.push(await request.json())
+          return new HttpResponse(null, { status: 204 })
+        },
+      })
+
+      customRender(<RealtimeSettings />)
+
+      const maxConcurrentUsersInput = await screen.findByLabelText('Max concurrent clients')
+      await userEvent.clear(maxConcurrentUsersInput)
+      await userEvent.type(maxConcurrentUsersInput, value)
+
+      fireEvent.click(screen.getByRole('button', { name: 'Save changes' }))
+
+      if (accepted) {
+        const dialog = await screen.findByRole('dialog')
+        fireEvent.click(within(dialog).getByRole('button', { name: 'Save changes' }))
+
+        await waitFor(() => expect(requests).toHaveLength(1))
+        expect(requests[0]).toMatchObject({ max_concurrent_users: Number(value) })
+      } else {
+        expect(
+          await screen.findByText('Cannot exceed 300,000 concurrent clients')
+        ).toBeInTheDocument()
+        expect(screen.queryByRole('dialog')).not.toBeInTheDocument()
+        expect(requests).toHaveLength(0)
+      }
+    }
+  )
+
+  test('rejects max concurrent clients above the entitlement when it is below the soft limit', async () => {
+    customRender(<RealtimeSettings />)
+
+    const maxConcurrentUsersInput = await screen.findByLabelText('Max concurrent clients')
+    await userEvent.clear(maxConcurrentUsersInput)
+    await userEvent.type(maxConcurrentUsersInput, '50001')
+
+    fireEvent.click(screen.getByRole('button', { name: 'Save changes' }))
+
+    expect(await screen.findByText('Cannot exceed 50,000 concurrent clients')).toBeInTheDocument()
+    expect(screen.queryByRole('dialog')).not.toBeInTheDocument()
+  })
 })

apps/studio/components/interfaces/Realtime/RealtimeSettings.tsx

@@ -44,7 +44,7 @@ import { useSelectedProjectQuery } from '@/hooks/misc/useSelectedProject'
 const formId = 'realtime-configuration-form'
 
 const REALTIME_SOFT_LIMITS = {
-  max_concurrent_users: 50_000,
+  max_concurrent_users: 300_000,
   max_events_per_second: 50_000,
   max_presence_events_per_second: 5_000,
   max_payload_size_in_kb: 3_000,