Refactor get_metadata_compute_strategy to not depend on `app`.

This allows me to claim galaxy-job-execution doesn't depend on ``app``.

lib/galaxy/jobs/__init__.py

@@ -875,7 +875,7 @@ class JobWrapper(HasResourceParameters):
         self.output_hdas_and_paths = None
         self.tool_provided_job_metadata = None
         # Wrapper holding the info required to restore and clean up from files used for setting metadata externally
-        self.external_output_metadata = get_metadata_compute_strategy(self.app, job.id)
+        self.external_output_metadata = get_metadata_compute_strategy(self.app.config, job.id)
         self.job_runner_mapper = JobRunnerMapper(self, queue.dispatcher.url_to_destination, self.app.job_config)
         self.params = None
         if job.params:

lib/galaxy/metadata/__init__.py

@@ -20,8 +20,8 @@ log = getLogger(__name__)
 SET_METADATA_SCRIPT = 'from galaxy_ext.metadata.set_metadata import set_metadata; set_metadata()'
 
 
-def get_metadata_compute_strategy(app, job_id):
-    metadata_strategy = app.config.metadata_strategy
+def get_metadata_compute_strategy(config, job_id):
+    metadata_strategy = config.metadata_strategy
     if metadata_strategy == "legacy":
         return JobExternalOutputMetadataWrapper(job_id)
     else:

lib/galaxy/tools/__init__.py

@@ -2394,7 +2394,7 @@ class SetMetadataTool(Tool):
             job, base_dir='job_work', dir_only=True, obj_dir=True
         )
         for name, dataset in inp_data.items():
-            external_metadata = get_metadata_compute_strategy(app, job.id)
+            external_metadata = get_metadata_compute_strategy(app.config, job.id)
             sa_session = app.model.context
             if external_metadata.external_metadata_set_successfully(dataset, name, sa_session, working_directory=working_directory):
                 external_metadata.load_metadata(dataset, name, sa_session, working_directory=working_directory)

lib/galaxy/tools/actions/metadata.py

@@ -78,7 +78,7 @@ class SetMetadataToolAction(ToolAction):
         job_working_dir = app.object_store.get_filename(job, base_dir='job_work', dir_only=True, extra_dir=str(job.id))
         datatypes_config = os.path.join(job_working_dir, 'registry.xml')
         app.datatypes_registry.to_xml_file(path=datatypes_config)
-        external_metadata_wrapper = get_metadata_compute_strategy(app, job.id)
+        external_metadata_wrapper = get_metadata_compute_strategy(app.config, job.id)
         output_datatasets_dict = {
             dataset_name: dataset,
         }

test/unit/tools/test_metadata.py

@@ -143,7 +143,7 @@ class MetadataTestCase(unittest.TestCase, tools_support.UsesApp, tools_support.U
             f.write(contents)
 
     def metadata_command(self, output_datasets):
-        metadata_compute_strategy = get_metadata_compute_strategy(self.app, self.job.id)
+        metadata_compute_strategy = get_metadata_compute_strategy(self.app.config, self.job.id)
         self.metadata_compute_strategy = metadata_compute_strategy
 
         exec_dir = None