docs: decision record about project structure review (#1803)

* docs: decision record about project structure review

* pr remarks

docs/developer/decision-records/2022-08-09-project-structure-review/README.md

@@ -0,0 +1,55 @@
+# Title of the Decision Record
+
+## Decision
+
+The project structure needs to be changed, to follow a "component" structure.
+
+## Rationale
+
+Currently it's hard for a new developer or adopter to understand the different components of the application are composed, in particular 
+`control-plane`, `data-plane`, `federated-catalog` etc...
+
+> A component is a particular EDC combination of dependencies that respond to a particular need, e.g.: `control-plane`, `data-plane`, `data-plane-selector`.
+This would help developers to orient themselves in the codebase more easily and separate responsibilities in a better way.
+
+The goal of this review is to have a clearer structure.
+
+## Approach
+
+### Spi
+The `spi` module should be refactored as:
+```
+spi/common/catalog-spi
+spi/common/core-spi
+spi/common/transport-spi
+spi/common/web-spi
+spi/control-plane
+spi/control-plane/asset-spi
+spi/control-plane/contract-spi
+spi/control-plane/policy-spi
+spi/control-plane/transfer-spi
+spi/data-plane/data-plane-spi
+spi/data-plane/data-plane-selector-spi
+```
+Every component should have its own `spi` module, then other "common" spi could exist as well (like `core`, `catalog`, `transport` and `web`)
+
+Some details:
+- the `asset-spi` would be extracted from the `core-spi`
+- the `*Service` interfaces should be moved to the `control-plane/*-spi`
+
+### Core
+The responsibility of the core modules is to provide a working base version of every component, so they should provide
+a default implementation for every interface present in the relative `spi` module, so these three modules will be introduced:
+- `control-plane-core`: would contain all the default implementations of the stores and the services and an extension that register them as default
+- `data-plane-core`: is the current `data-plane-framework` extension, will register all the default implementations
+- `data-plane-selector-core`: is the current `selector-core` module
+
+All of them should extend the `base-core` module. The `defaults` module would probably disappear (replaced by the `<component>-core` ones)
+
+### Extensions
+
+This component separation will be put in place also in the `extensions` folder, as some extensions are needed only by one of the components, for example:
+- `control-plane`: data management api, provisioners (s3, blobstorage, http...), "stores" sql/cosmos implementations (for assets, contracts, transfer process, policies...), data-plane-selector client, ...
+- `data-plane`: implementations of the source/sink interfaces like `data-plane-http`, `data-plane-s3`, etc.., data plane specific api (`data-plane-api` module)
+- `data-plane-selector`: implementations of the `DataPlaneInstanceStore`
+- common (needed by more than one component): observability api, vault, configuration, http, loggers, iam, ...

docs/developer/decision-records/README.md

@@ -28,4 +28,5 @@
 - [2022-07-27 Custom DTO validation](2022-07-27-custom-dto-validation/README.md)
 - [2022-07-28 "Provisioning Requested" TransferProcess new state](2022-07-28-transfer-process-new-state/README.md)
 - [2022-08-01 Entity Timestamp](2022-08-01-entity-timestamp/README.md)
-- [2022-08-04 Automated Documentation](developer/decision-records/2022-08-04-documentation-automation/README.md)
+- [2022-08-04 Automated Documentation](2022-08-04-documentation-automation/README.md)
+- [2022-08-09 Project structure review](2022-08-09-project-structure-review/README.md)