docs: enhance GraphQL schema documentation

- Added comprehensive descriptions to all types, interfaces, and fields in 'schema/api_commons.graphql'.

- Improved documentation for mutations and input/response types in 'schema/mutations.graphql'.

- Added detailed descriptions for all queries and their arguments in 'schema/queries.graphql'.

- Enhanced documentation for core Zabbix types and enums in 'schema/zabbix.graphql'.

- Updated extension schemas under 'schema/extensions/' with proper GraphQL descriptions.

- Verified schema validity via 'graphql-codegen' and ran all tests to ensure consistency.

schema/extensions/location_tracker_commons.graphql

@@ -27,6 +27,9 @@ type SensorDistanceValue implements DeviceValue {
     """
     time: String
 
+    """
+    Dummy field to allow for empty interfaces.
+    """
     _empty: String
 }
 
@@ -34,8 +37,11 @@ type SensorDistanceValue implements DeviceValue {
 Represents a coordinate in 3D space with x, y, and z components.
 """
 type Position {
+    """X coordinate."""
     x: Float
+    """Y coordinate."""
     y: Float
+    """Z coordinate."""
     z: Float
 }
 
@@ -43,7 +49,9 @@ type Position {
 Represents the result of a position calculation, including the calculated position and accuracy.
 """
 type PositionCalculatorResult {
+    """The calculated 3D position."""
     position: Position
+    """The estimated accuracy of the calculation."""
     accuracy: Float
 }
 
@@ -51,10 +59,16 @@ type PositionCalculatorResult {
 Concrete implementation of a DeviceValueMessage for sensor distance data.
 """
 type SensorDistanceMessage implements DeviceValueMessage {
+    """The unique identifier of the device."""
     deviceKey: String
+    """Timestamp of the message."""
     timestamp: String
+    """Name of the attribute."""
     attributeName: String
+    """Name of the topic."""
     topicName: String
+    """Type of the device."""
     deviceType: String
+    """The sensor distance value payload."""
     value: SensorDistanceValue
 }