States the maintained versions (#711)

Closes #658

CHANGES.md

@@ -2,6 +2,7 @@
 
 ## Version 5.0.5
 
+* State what versions are maintained - Issue #658
 * Investigate Java 17 - Issue #607
 * RetryPolicy: After failing the last connection attempt, the retry time is still applied - Issue #702
 * Define logging levels formally - Issue #666

docs/COMPATIBILITY.md

@@ -1,9 +1,9 @@
 # Compatibility
 
-Below matrix defines which ecChronos versions have been tested and verified with which Cassandra version.
 
-| ecchronos version      | Cassandra 3.0.X | Cassandra 3.11.X | Cassandra 4.0.X | Cassandra 4.1.X | Cassandra 5.0-alpha1 |
-|------------------------|-----------------|------------------|-----------------|-----------------|----------------------|
-| <= 2.0.5            | X               | X                |                 |                 |                      |
-| > 2.0.5  < 5.0.0 | X               | X                | X               |                 |                      |
-| >= 5.0.0            |                 |                  | X               | X               | X                    |
+The table below shows what versions of Cassandra have been verified with ecChronos releases. 
+
+| ecChronos  | 3.0.x | 3.11.x | 4.0.x | 4.1.x | 5.0-alpha1 |
+|:----------:|:-----:|:------:|:-----:|:-----:|:----------:|
+|   4.x.x    |   X   |   X    |   X   |   -   |     -      |
+|   5.x.x    |   -   |   -    |   X   |   X   |     X      |

docs/CONTRIBUTING.md

@@ -66,6 +66,18 @@ If you encounter a PMD rule that seems odd or non-relevant feel free to discuss
 * [Maven](https://maven.apache.org) - Dependency and build management
 * [docker-maven-plugin](https://github.com/fabric8io/docker-maven-plugin) - For integration tests
 
+### Maintained versions
+
+The following table state what versions of ecChronos is still under active maintenance.
+
+| Version | First Release | Status |
+|:-------:|:-------------:|:------:|
+|  1.x.x  |  2019-Jan-25  |   -    |
+|  2.x.x  |  2021-Feb-25  |   -    |
+|  3.x.x  |  2022-Jun-30  |   -    |
+|  4.x.x  |  2022-Dec-15  |   X    |
+|  5.x.x  |  2023-Dec-06  |   X    |
+
 ### REST API
 
 Whenever there are any changes to the REST API, the OpenAPI specification must be generated.