This pull request introduces a new external control API, allowing other apps or services to query, update, and trigger actions on Essentials features and settings through a permission-protected interface. It defines a new dangerous permission, adds a content provider and broadcast receiver, and implements a modular routing system for handling external requests. The initial handlers support querying/updating app settings and controlling location alarms.

External Control API infrastructure:

• Added a new dangerous permission (com.sameerasw.essentials.permission.EXTERNAL_CONTROL) and a permission group to the manifest, with appropriate user-facing labels and descriptions. [1] [2]
• Declared a new ExternalControlProvider (content provider) and ExternalActionReceiver (broadcast receiver) in the manifest, both protected by the new permission.
• Implemented ExternalControlProvider to handle external queries, updates, and actions via the content provider interface, delegating to a routing system.
• Implemented ExternalActionReceiver to handle external broadcast actions, also delegating to the routing system.

Routing and handler design:

• Introduced the ExternalHandler interface and ExternalRouter singleton to register and route requests to feature-specific handlers based on path. [1] [2]

Feature-specific external handlers:

• Added SettingsExternalHandler to allow querying, updating, and toggling of app settings externally.
• Added LocationAlarmExternalHandler to support querying alarms and starting/stopping location alarm features externally.