[🐴] DM button on profile (#4097)

* add profile button

* separate out button to component

* normalise subscribe to labeller button size

* infinite staletime

* use Link rather than Button and change icon

* adjust icon position

src/state/queries/messages/get-convo-for-members.ts

@@ -1,11 +1,15 @@
 import {ChatBskyConvoGetConvoForMembers} from '@atproto/api'
-import {useMutation, useQueryClient} from '@tanstack/react-query'
+import {useMutation, useQuery, useQueryClient} from '@tanstack/react-query'
 
 import {logger} from '#/logger'
 import {DM_SERVICE_HEADERS} from '#/state/queries/messages/const'
 import {useAgent} from '#/state/session'
+import {STALE} from '..'
 import {RQKEY as CONVO_KEY} from './conversation'
 
+const RQKEY_ROOT = 'convo-for-user'
+export const RQKEY = (did: string) => [RQKEY_ROOT, did]
+
 export function useGetConvoForMembers({
   onSuccess,
   onError,
@@ -35,3 +39,29 @@ export function useGetConvoForMembers({
     },
   })
 }
+
+/**
+ * Gets the conversation ID for a given DID. Returns null if it's not possible to message them.
+ */
+export function useMaybeConvoForUser(did: string) {
+  const {getAgent} = useAgent()
+
+  return useQuery({
+    queryKey: RQKEY(did),
+    queryFn: async () => {
+      const convo = await getAgent()
+        .api.chat.bsky.convo.getConvoForMembers(
+          {members: [did]},
+          {headers: DM_SERVICE_HEADERS},
+        )
+        .catch(() => ({success: null}))
+
+      if (convo.success) {
+        return convo.data.convo.id
+      } else {
+        return null
+      }
+    },
+    staleTime: STALE.INFINITY,
+  })
+}