refactor: Accept nulls for optional entity fields

[scottlovegrove]

Fixes: #133

Fields that weren't being returned in v1 of the REST API may now be returned but have a value of null. Our validation wasn't catering for that. Have updated the partial types to accept the type or NULL.

There were a few other instances of number-based ID usage that hadn't been switched. These have now been corrected.

Testing

You can try and follow the instructions in the readme using the scratch.ts file in order to test this.

import { TodoistApi } from './TodoistApi'

const token = '<TOKEN>'

const api = new TodoistApi(token)

async function doIt() {
    try {
        const projects = await api.getProjects()
        console.log(projects.length)
    } catch (error: unknown) {
        if (error instanceof Error) {
            console.log(error)
        }
        console.log({ error })
    }
}

doIt().catch(() => {
    // noop
})

I found putting breakpoints on the console.logs allowed me to see the problem. Prior to the fix, the ones in the catch would get hit, post-fix, the one inside the try would get hit.

I have updated all the tests to account for all of the partial/nulls though.

[craigcarlyle]

Code changes look reasonable and test plan works as expected 🚀