Use readonly db connection for getRepo

pegasus/lib/api/sync/getRepo.ml

···
 let handler =
   Xrpc.handler (fun ctx ->
       let {did; _} = Xrpc.parse_query ctx.req params_of_yojson in
-      let%lwt repo = Repository.load did ~ensure_active:true in
+      let%lwt user_db = User_store.connect_readonly did in
+      let%lwt repo = Repository.load did ~ensure_active:true ~user_db in
       let%lwt car_stream = Repository.export_car repo in
       Dream.stream
         ~headers:[("Content-Type", "application/vnd.ipld.car")]

pegasus/lib/data_store.ml

···
               pool := Some db ;
               Lwt.return db )
 
+let connect_readonly ?create () =
+  if create = Some true then
+    Util.mkfile_p Util.Constants.pegasus_db_filepath ~perm:0o644 ;
+  let%lwt db =
+    Util.connect_sqlite ?create ~write:false Util.Constants.pegasus_db_location
+  in
+  let%lwt () = Migrations.run_migrations Data_store db in
+  Lwt.return db
+
 let create_actor ~did ~handle ~email ~password ~signing_key conn =
   let password_hash = Bcrypt.hash password |> Bcrypt.string_of_hash in
   let now = Util.now_ms () in

pegasus/lib/repository.ml

···
   in
   Lwt.return {commit= new_commit; results}
 
-let load ?create ?(ensure_active = false) did : t Lwt.t =
+let load ?create ?(ensure_active = false) ?user_db did : t Lwt.t =
   let%lwt ds_conn = Data_store.connect () in
   let%lwt user_db =
-    try%lwt User_store.connect ?create did
-    with _ ->
-      Errors.invalid_request ~name:"RepoNotFound"
-        "your princess is in another castle"
+    match user_db with
+    | Some db ->
+        Lwt.return db
+    | None -> (
+      try%lwt User_store.connect ?create did
+      with _ ->
+        Errors.invalid_request ~name:"RepoNotFound"
+          "your princess is in another castle" )
   in
   let%lwt actor =
     match%lwt Data_store.get_actor_by_identifier did ds_conn with

pegasus/lib/user_store.ml

···
               Hashtbl.replace pool_cache did t ;
               Lwt.return t )
 
+let connect_readonly ?create did =
+  if create = Some true then
+    Util.mkfile_p (Util.Constants.user_db_filepath did) ~perm:0o644 ;
+  let%lwt db =
+    Util.connect_sqlite ?create ~write:false
+      (Util.Constants.user_db_location did)
+  in
+  let%lwt () = Migrations.run_migrations User_store db in
+  Lwt.return {did; db}
+
 (* mst blocks; implements Writable_blockstore *)
 
 let get_bytes t cid : Blob.t option Lwt.t =
···
   if List.is_empty entries then Lwt.return_ok 0
   else
     Lwt_result.catch (fun () ->
-        let%lwt () = Util.use_pool t.db (fun conn -> Bulk.put_blocks entries conn) in
+        let%lwt () =
+          Util.use_pool t.db (fun conn -> Bulk.put_blocks entries conn)
+        in
         Lwt.return (List.length entries) )
 
 let delete_block t cid : (bool, exn) Lwt_result.t =