fix metadata for apply_dimension with target

CHANGELOG.md

@@ -15,6 +15,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- apply_dimension with a 'target_dimension' argument was not correctly adjusting datacube metadata on the client side, causing a mismatch.
+
 
 ## [0.31.0] - 2024-07-26
 

openeo/rest/datacube.py

@@ -1160,11 +1160,16 @@ def apply_dimension(
             "process": process,
             "dimension": self._assert_valid_dimension_name(dimension),
         }
+
+        metadata = self.metadata
         if target_dimension is not None:
             arguments["target_dimension"] = target_dimension
+            metadata = self.metadata.reduce_dimension(dimension_name=dimension) if self.metadata else None
+            if(not target_dimension in self.metadata.dimension_names()):
+                metadata = self.metadata.add_dimension(target_dimension, label="unknown")
         if context is not None:
             arguments["context"] = context
-        result_cube = self.process(process_id="apply_dimension", arguments=arguments)
+        result_cube = self.process(process_id="apply_dimension", arguments=arguments, metadata = metadata)
 
         return result_cube