TODO: remove.

TokensConfigName is the user-supplied name for this token type.

TokensConfigPlugin is the connector plugin used for this token type.

Capabilities is the supported featureset of the tokens interface implemented by the plugin, with the specified config.

TokenPool is the set of data returned from the connector when a token pool is created.

Callbacks is the interface provided to the tokens plugin, to allow it to pass events back to firefly.

Plugin is the interface implemented by each tokens plugin.