fix: Signup error redirect to wrong path (#31179)

On signup failure, we need to redirect the client to same signup page
they were on, for the error message to show up. So instead of
redirecting to the homepage, we get the path from the incoming request
and use that.

app/server/appsmith-server/src/main/java/com/appsmith/server/solutions/ce/UserSignupCEImpl.java

@@ -219,10 +219,21 @@ public Mono<Void> signupAndLoginFromFormData(ServerWebExchange exchange) {
                 .flatMap(user -> signupAndLogin(user, exchange))
                 .then()
                 .onErrorResume(error -> {
+                    String path = "/user/signup";
+
+                    String referer = exchange.getRequest().getHeaders().getFirst("referer");
+                    if (referer != null) {
+                        try {
+                            path = URI.create(referer).getPath();
+                        } catch (IllegalArgumentException ex) {
+                            // This is okay, we just use the default value for `path`.
+                        }
+                    }
+
                     URI redirectUri;
                     try {
                         redirectUri = new URIBuilder()
-                                .setPath("/")
+                                .setPath(path)
                                 .setParameter("error", error.getMessage())
                                 .build();
                     } catch (URISyntaxException e) {