[thesuzerain]

• Removes build_memory in factor of defaulting to in-memory databases and allowing .database(path) to be passed
• Matches parity between AdsStore and HttpCache for functionality like (former) build_memory and open_db
• Flattens adsstore/httpstore generation in client.rs to not branch into multiple builders.

Should be no breaking changes (though obviously httpcache is 'touched', and should be covered by tests).

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[thesuzerain]

This solution is a little bit uglier than the previous in that its more LoC (when formatted, at least), and the repeated cache_config.as_ref()

But its flatter and does not require multiple builders (as it would if you do if let Some(config) = config or some other uglier workarounds.

Another option I elected against was adding a Default implementation for AdsCacheConfig- which clears out the need for the repeated .cache_config.as_ref(), but since we have a non-optional field it feels like a bit of a smell (and I prefer keeping that field mandatory.

I can also revert it to the former logic which is essentially:

if let Some(config) = config {
    // calculate defaults
   let x = default_x_y_z;
   Builder::builder().with().arguments()
} else {
   Builder::builder().default().if().no().config().passed()
}