[ETHEREUM-CONTRACTS] GDA storage layout refactoring (#2086)

Author: hellwolf

.github/workflows/daily-slack-message.yml

@@ -3,6 +3,14 @@ All notable changes to the ethereum-contracts will be documented in this file.
 
 This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [UNRELEASED]
+
+### Changed
+- Refactored `GeneralDistributionAgreementV1`: extracted functionality which reads and writes agreement data to from/to the token contract into dedicated libraries:
+  - `GDAv1StorageLib` contains data structures and related encoders/decoders.
+  - `GDAv1StorageReader` contains getters reading agreement data from the token contract, allowing contracts to get this data without making a call to the GDA contract.
+  - `GDAv1StorageWriter` contains functions for writing agreement data to the token contract. This can only be used by the GDA contract itself.
+
 ## [v1.13.0]
 
 ### Added