MongoDB Stitch (MongoDB’s functions-as-a-service product) isn’t on the list of supported providers at https://serverless.com/framework/docs/#Supported-Providers.
Is support planned for Stitch in the near future, where “support” would mean publishing functions to Stitch Functions (https://docs.mongodb.com/stitch/functions/) instead of AWS Lambda?
If not, who usually builds hosting provider integrations: Serverless or the hosting provider? In other words, do I have to ask MongoDB to build it? 
Also if there’s no existing MongoDB Stitch function deployment support, can I build it myself? If yes, what’s a good sample and/or docs to get started?