Refactor confirm to avoid passing closures

src/app/components/SpaceJoinConfirm.svelte

@@ -0,0 +1,32 @@
+<script module lang="ts">
+  import {goto} from "$app/navigation"
+  import {makeSpacePath} from "@app/routes"
+  import {addSpaceMembership} from "@app/commands"
+  import {pushToast} from "@app/toast"
+
+  export const confirmSpaceJoin = async (url: string) => {
+    await addSpaceMembership(url)
+
+    goto(makeSpacePath(url), {replaceState: true})
+
+    pushToast({
+      message: "Welcome to the space!",
+    })
+  }
+</script>
+
+<script lang="ts">
+  import Confirm from "@lib/components/Confirm.svelte"
+
+  type Props = {
+    url: string
+  }
+
+  const {url}: Props = $props()
+
+  const confirm = () => confirmSpaceJoin(url)
+</script>
+
+<Confirm
+  {confirm}
+  message="This space does not appear to limit who can post to it. This can result in a large amount of spam or other objectionable content. Continue?" />