fix(polar): Cannot read properties of undefined (reading 'type')

[robingenz]

Description

The following error message appears when I retrieve sponsorships from Polar (see this run):

[info] Fetching sponsorships from polar...
TypeError: Cannot read properties of undefined (reading 'type')
    at file:///home/runner/work/static/static/node_modules/sponsorkit/dist/shared/sponsorkit.ccaa557f.mjs:1055:37
    at Array.map (<anonymous>)
    at fetchPolarSponsors (file:///home/runner/work/static/static/node_modules/sponsorkit/dist/shared/sponsorkit.ccaa557f.mjs:1048:53)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async run (file:///home/runner/work/static/static/node_modules/sponsorkit/dist/cli.mjs:143:22)
    at async Object.handler (file:///home/runner/work/static/static/node_modules/sponsorkit/dist/cli.mjs:367:5)
Error: Process completed with exit code 1.

It seems like subscription_tier was an internal property which has just been removed. This is the API documentation: https://api.polar.sh/redoc#tag/subscriptions/operation/subscriptions:search_subscriptions

Linked Issues

Additional context

[birkjernstrom]

Wow fantastic work & quick catch @robingenz ! Sorry about this causing a breaking implementation.

We're introducing products soon and have consolidated subscriptions & products into one entity with different prices/intervals. I apologies for the breaking change. We're making some big investments into our API in the coming months(s) as we're expanding our product towards a v1.0 this year. Later, we'll definitely introduce versioning to avoid breaking changes causing actual breakages immediately.

[robingenz]

@antfu It would be great if we could merge this quick fix.