Update create API

[rushmorem]

What is the motivation?

#4667 made sure create always returns a single object.

What does this change do?

This is a followup to that PR to make sure the API always expects a single record. To create on a record ID, one does

let person: Option<Person> = db.create(("person", "tobie")).await?;

This hasn't changed. To call create on a table we used to do

let person: Vec<Person> = db.create("person").await?;

This is what has changed. Now we do

let person: Option<Person> = db.create("person").await?;

Notice the difference in return type.

We had an opportunity here to go back to what we were doing before v1.

let person: Person = db.create("person").await?;

This would have been nice but then code like

db.create("person").await?;

would compile fine because in that case, Rust infers the return type to be a unit.

What is your testing strategy?

Github Actions.

Is this related to any issues?

• No related issues

Does this change need documentation?

surrealdb/docs.surrealdb.com#820

Have you read the Contributing Guidelines?

• I have read the Contributing Guidelines