Some fixes related to logs and DB funcs

Created by: oblivisheee

This pull request introduces several improvements to the subscription service, including updates to dependencies, enhancements to SQL functions, and the addition of tracing for better observability. The most significant changes are outlined below:

Dependency Updates:

• Updated tracing-subscriber to include the env-filter feature in subscription/Cargo.toml.
• Added tracing-loki dependency in subscription/Cargo.toml.

SQL Function Enhancements:

• Modified SQL functions in subscription/sql/funcs_plans.surql and subscription/sql/funcs_subs.surql to use RETURN statements for better consistency and clarity. [1] [2]

Tracing and Instrumentation:

• Added instrument macros and info logs in subscription/src/db.rs to enhance observability for database operations. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]

Interface Enhancements:

• Added info, warn, and error logs in subscription/src/interfaces.rs to improve the visibility of operations such as fetching, creating, updating, and deleting plans and subscribers. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]