Add development roadmap

src/site/markdown/development.md

@@ -64,5 +64,6 @@ The current build status for the master branch:
 
 ## Further Documentation
 
+* [Roadmap](development/roadmap.md)
 * [Caching](development/caching.md)
 * [Event System](development/event-system.md)

src/site/markdown/development/roadmap.md

+# Roadmap
+
+## 4.0
+
+* Remove API v2 compatibility layer
+
+
+## 3.1
+
+TBD
+
+
+## 3.0
+
+Version 3.0 is a rewrite of large parts of the code base with the goal of improving its maintainability.
+A new streamlined REST API is developed while the legacy API is still supported through a compatibility layer.
+
+
+### Beta 2
+
+## Deployment & Operations
+
+* Implement a monitoring endpoint for Prometheus
+
+
+## Documentation
+
+* Create/update developer documentation
+	* REST API
+	* Architecture
+	* Coding guidelines
+* Update installation and upgrade guide
+
+
+## QA
+
+* Review critical issues detected by static code analysis
+
+
+### Beta 1
+
+## General architecture
+
+* Implement data validation for entities
+* Use better caching implementation (Ehcache, etc.)
+* Review and complete caching (annotations, keys, etc.)
+* Review and complete authorization handling
+* Review event system and unify emitting of events for CRUD operations
+	* https://spring.io/blog/2015/02/11/better-application-events-in-spring-framework-4-2
+* Review and improve error handling
+	* Exceptions
+	* HTTP responses
+	* Logging
+* Use modern logging framework (SLF4J with Logback instead of Log4j)
+
+
+## REST API
+
+* Adjust handling of non-persistent entities for API v3
+* Reimplement export and import
+
+
+## QA
+
+* Increase code coverage for testing
+* Implement performance tests (Gattling)
+* Ensure Java 11 (LTS) compatibility
+* Review blocker issues detected by static code analysis
+
+
+### Alpha
+
+## General architecture
+
+* Minimize code duplication
+	* Use generic classes for entity related controllers, services and data repositories
+* Prefer constructor injection for required dependencies
+	* Use setter injection for optional dependencies
+	* Avoid field injection (it's fine in test classes)
+* Use Jackson's JsonViews to define property visibility for API and persistence
+* Refactor entities
+	* Introduce abstract Entity class with common properties
+	* Improve nomenclature for class and property naming
+		* Avoid use-case specific names (such as "Peer Instruction" for multiple rounds)
+		* Session -> Room
+		* Lecture Question -> Content
+		* Audience Question -> Comment
+		* Learning Progress -> Score
+		* Question Type -> Content Format
+	* Do not reuse one entity type for multiple domain types
+		* `Question` -> split up into `Content`, `Comment`
+		* `Answer` -> split up into `Answer`, `AnswerStatistics`
+	* Use subclasses to implement different formats for Content and Answer
+
+
+## Persistence
+
+* Abstract and split up persistence layer with help of Spring Data interfaces
+* Get rid of JSON-lib (buggy and unmaintained) and use Jackson for all JSON (de-)serialization
+* Use Ektorp instead of CouchDB4J (buggy and unmaintained) for CouchDB handling
+* Implement view creation and data migration in Java (replace Setup Tool used for 2.x)
+* Merge redundant database views
+* Avoid emitting full docs and use `include_docs` instead
+
+
+## REST API
+
+* Implement support for handling multiple API versions
+* Implement API v3
+	* Stateless: No more `/whoami` or `/myxyz` routes
+	* Use JWT instead of cookie-based sessions for authentication
+	* Use generic routes for CRUD
+		* Implement HTTP PATCH to update properties
+		* No more `/<entity>/disablexyz`
+	* Implement a `/<entity type>/find` endpoint
+	* Provide statistics with non-aggregated combinations of answer choices
+	* Implement customizable content groups
+			* They replace predefined content variants
+			* Relations are stored as part of a room
+			* They support auto sort (v2 behavior) and user defined ordering
+* Implement API live migration layer v2 <-> v3
+	* v2 controllers convert between v2 and v3 entity types
+	* Internally (service and persistence layer) only the v3 entity type is used