* chore: bump browserslist-db@latest
* refactor(EndpointService): simplify with `generateConfig`, utilize optional baseURL for OpenAI-based endpoints, use `isUserProvided` helper fn wherever needed
* refactor(custom/initializeClient): use standardized naming for common variables
* feat: user provided baseURL for openAI-based endpoints
* refactor(custom/initializeClient): re-order operations
* fix: knownendpoints enum definition and add FetchTokenConfig, bump data-provider
* refactor(custom): use tokenKey dependent on userProvided conditions for caching and fetching endpointTokenConfig, anticipate token rates from custom config
* refactor(custom): assure endpointTokenConfig is only accessed from cache if qualifies for fetching
* fix(ci): update tests for initializeClient based on userProvideURL changes
* fix(EndpointService): correct baseURL env var for assistants: `ASSISTANTS_BASE_URL`
* fix: unnecessary run cancellation on res.close() when response.run is completed
* feat(assistants): user provided URL option
* ci: update tests and add test for `assistants` endpoint
* chore: leaner condition for request closing
* chore: more descriptive error message to provide keys again
