feat: avoid sorting for MakeSelfOnTop

- Although sorting can be used to make the doer the first user of the
list, this isn't optimal and can be instead done with a linear search,
remove that entry and add the doer to the front of the slice.
- Extra unit test added.

routers/web/repo/helper_test.go

@@ -23,4 +23,15 @@ func TestMakeSelfOnTop(t *testing.T) {
 	users = MakeSelfOnTop(&user.User{ID: 2}, []*user.User{{ID: 2}, {ID: 1}})
 	assert.Len(t, users, 2)
 	assert.EqualValues(t, 2, users[0].ID)
+
+	users = MakeSelfOnTop(&user.User{ID: 2}, []*user.User{{ID: 1}})
+	assert.Len(t, users, 1)
+	assert.EqualValues(t, 1, users[0].ID)
+
+	users = MakeSelfOnTop(&user.User{ID: 2}, []*user.User{{ID: 1}, {ID: 2}, {ID: 3}, {ID: 4}})
+	assert.Len(t, users, 4)
+	assert.EqualValues(t, 2, users[0].ID)
+	assert.EqualValues(t, 1, users[1].ID)
+	assert.EqualValues(t, 3, users[2].ID)
+	assert.EqualValues(t, 4, users[3].ID)
 }