feat: Show RegistrationsDisabled on login page

public/locales/en-US/signup.json

@@ -14,5 +14,10 @@
         "continueActionLabel": "Yes, edit email"
       }
     }
+  },
+  "registrationsDisabled": {
+    "title": "Registrations are disabled",
+    "description": "We are sorry, but registrations on this instance are disabled.",
+    "login": "Login"
   }
 }

src/route-widgets/SignupRoute/RegistrationsDisabled.tsx

@@ -0,0 +1,40 @@
+import {ReactElement} from "react"
+import {Link} from "react-router-dom"
+import {useTranslation} from "react-i18next"
+
+import {Box, Button, Grid, Paper, Typography} from "@mui/material"
+
+export default function RegistrationsDisabled(): ReactElement {
+	const {t} = useTranslation("signup")
+
+	return (
+		<Paper>
+			<Box maxWidth="sm">
+				<Grid
+					container
+					spacing={4}
+					padding={4}
+					alignItems="center"
+					justifyContent="center"
+					flexDirection="column"
+				>
+					<Grid item>
+						<Typography variant="h4" align="center">
+							{t("registrationsDisabled.title")}
+						</Typography>
+					</Grid>
+					<Grid item>
+						<Typography variant="body1" align="center">
+							{t("registrationsDisabled.description")}
+						</Typography>
+					</Grid>
+					<Grid item>
+						<Button component={Link} to="/auth/login" variant="contained">
+							{t("registrationsDisabled.login")}
+						</Button>
+					</Grid>
+				</Grid>
+			</Box>
+		</Paper>
+	)
+}

src/routes/SignupRoute.tsx

@@ -5,6 +5,7 @@ import {useLoaderData} from "react-router-dom"
 import {MultiStepForm} from "~/components"
 import {ServerSettings} from "~/server-types"
 import EmailForm from "~/route-widgets/SignupRoute/EmailForm"
+import RegistrationsDisabled from "~/route-widgets/SignupRoute/RegistrationsDisabled"
 import YouGotMail from "~/route-widgets/SignupRoute/YouGotMail"
 
 export default function SignupRoute(): ReactElement {
@@ -13,6 +14,10 @@ export default function SignupRoute(): ReactElement {
 
 	const index = email ? 1 : 0
 
+	if (!serverSettings.allowRegistrations) {
+		return <RegistrationsDisabled />
+	}
+
 	return (
 		<MultiStepForm
 			steps={[

src/server-types.ts

@@ -85,6 +85,7 @@ export interface ServerSettings {
 	publicKey: string
 	allowAliasDeletion: boolean
 	apiKeyMaxDays: number
+	allowRegistrations: boolean
 }
 
 export interface Alias {