Cache provides an ephemeral cache for short-lived authentication tokens such as OAuth access and ID tokens and Firebase tokens. The cache contents are only stored in memory so are not preserved across executions.
This create is used by the Token Manager library.
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The TokenCache struct defines the cache as a map from CacheKey to TokenSet. CacheKey uniquely identifies a Service Provider account and the Auth Provider used to communicate with it, being composed of auth_provider_type and credential_id (aka user_profile_id). TokenSet contains a map for each of the possible short-lived token types.
The current nested cache structure is more complex and less flexible than necessary. We plan to migrate to a simpler design where each cache entry defines a single token.
Currently the cache does not handle expiry correctly if the maximum size is reached. Given the number of accounts, auth providers, and token types within the current products these limits are not being reached, but future work will correctly handle the size constraint.
The cache is a simple crate that is unlikely to ever be used outside of Token Manager. Potentially it will be merged into Token Manager at some point.