API key-based authentication for Semantic Layer Sync with Metabase

**Is your feature request related to a problem? Please describe.**
Currently, you have 2 options to connect Cube to Metabase, _Semantic Layer Sync_ and _SQL API_. But _Semantic Layer Sync_ asks for username+password which is not preferable way of integration after [Metabase API](https://www.metabase.com/learn/metabase-basics/administration/administration-and-operation/metabase-api) was released.

**Describe the solution you'd like**
Please, add support for Metabase API to connect Cube to Metabase.

**Describe alternatives you've considered**
[SQL API](https://cube.dev/blog/self-service-analytics-with-metabase-and-cube#integrate-metabase-and-cube) works. Though I can send queries, but the propagated models cannot be opened via GUI...


**Additional context**