[sujen1412]

Closes #12

Problem

hysds-ogc-container-builder writes optional: true with no default for File? / Directory? inputs. When the user leaves one empty, validate_job_submit drops it from the job, and map_inputs_from_context then:

• File?: calls os.path.basename(None) → TypeError, so the job fails before cwltool runs. A "" value instead produced a bogus {"class": "File", "path": "<cwd>"}.
• Directory?: calls load_json_from_uri(None), so STAC staging fails.

Change

Before the File / Directory branches in map_inputs_from_context:

• If the value is missing, "" or "None" (the same empty values convert_value_to_cwl_type treats as empty) and the type is optional → skip the input, so cwltool passes no flag to the algorithm.
• If the value is empty and the input is required → raise ValueError naming the input.

Primitive-type handling is unchanged.

Tests

New tests/test_create_inputs.py (19 tests):

• Empty optional File? / Directory? (both ["null", T] and T? forms; missing, "", "None") are omitted, and STAC staging isn't called.
• Empty required File / Directory raises.
• Provided optional File / Directory values still map and stage as before.
• Mixed inputs: other inputs are unaffected.

tests/test_create_inputs.py  19 passed

Note: tests/test_stage_in.py::TestStacMetadataPreservation has 2 failures (test_stac_extensions_preserved, test_self_href_set_to_local_path) that also fail on unmodified develop. They're unrelated to this change.