Serverless AWS Account Linking proxy providing OAuth2 access to PKCE-only services
The repo provides general Python3 code for the Lambda, and exported JSON of the API Gateway (which is really simple).
Amazon KMS is used as source of the secret, and SQS stores the global variable of the secret between lambda invocations. I use the proxy to enable account linking for an Alexa skill because the ASK does not support PKCE.