merge: Introduce schema for trace API (#88)

This pull request updates the OpenDC trace API to support proper specification 
of a schema of the tables exposed by the traces. This functionality makes it easier 
for the API consumer to understand the types exposed by the API.

## Implementation Notes :hammer_and_pick:

* Introduce type system for trace API
* Add benchmarks for odcvm trace format 
* Add benchmarks for Azure trace format
* Add conformance suite for OpenDC trace API 

## External Dependencies :four_leaf_clover:

* N/A

## Breaking API Changes :warning:

* Removal of typed `TableColumn`. Instead, `TableColumn` instances are now 
   used to describe the columns belonging to some table.
* `TableReader` and `TableWriter` do not support accessing arbitrary objects 
   anymore. Instead, only the types supported by the type system are exposed.

1 files changed, 4 insertions, 9 deletions

diff --git a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/Table.kt b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/Table.kt
index 05d0234a..e6e97706 100644
--- a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/Table.kt
+++ b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/Table.kt
@@ -32,21 +32,16 @@ public interface Table {
     public val name: String
 
     /**
-     * The list of columns supported in this table.
+     * The columns in this table.
      */
-    public val columns: List<TableColumn<*>>
-
-    /**
-     * The columns by which the table is partitioned.
-     */
-    public val partitionKeys: List<TableColumn<*>>
+    public val columns: List<TableColumn>
 
     /**
      * Open a [TableReader] for a projection of this table.
      *
-     * @param projection The list of columns to fetch from the table or `null` if no projection is performed.
+     * @param projection The names of the columns to fetch from the table or `null` if no projection is performed.
      */
-    public fun newReader(projection: List<TableColumn<*>>? = null): TableReader
+    public fun newReader(projection: List<String>? = null): TableReader
 
     /**
      * Open a [TableWriter] for this table.