Create an api for user Notes

### Proposal

I would like an API to be exposed to read and write user notes for books.

### Justification

This would be be a nice feature for people to build third party clients on or allow savvy users to modify their notes easily.

Personally, I would like to build a prototype of a UI to easily search and edit notes across many books so that's why I'm requesting this.

Honestly, most likely the impact is small. But you never know what someone might build with it.

### Breakdown

#### Requirements Checklist

* [ ] An API to read a user's notes
* [ ] An API to write notes for a user
* [ ] Both should be behind user auth

#### Related files

*Unsure

#### Stakeholders

*

#### Instructions for Contributors

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