We had this error in our neo4j pod recently:
```
2019-12-02 08:29:42.680+0000 ERROR Unable to schedule bolt session 'bolt-1018230' for execution since there are no available threads to serve it at the moment. You can retry at a later time or consider increasing max thread pool size for bolt connector(s).
2019-12-02 08:29:42.680+0000 ERROR Unable to schedule bolt session 'bolt-1018224' for execution since there are no available threads to serve it at the moment. You can retry at a later time or consider increasing max thread pool size for bolt connector(s).
2019-12-02 08:29:42.681+0000 ERROR Unable to schedule bolt session 'bolt-1018352' for execution since there are no available threads to serve it at the moment. You can retry at a later time or consider increasing max thread pool size for bolt connector(s).
2019-12-02 08:29:42.682+0000 ERROR Unable to schedule bolt session 'bolt-1018243' for execution since there are no available threads to serve it at the moment. You can retry at a later time or consider increasing max thread pool size for bolt connector(s).
```
Apparently the default is 400 threads. So we must have a leak somewhere.
Apparently, `neo4j-graphql-js` *replaces* the schema partly. When we use
join models like `EMOTED`, `neo4j-graphql-js` puts in a join model with
the two names of the connected types.
This commit takes all backend changes for signup and invite feature. I
was working on these features and removed the generated mutations for
type user along the way.
