Figure extraction from experiment data by name without extension (#1287)

### Summary

Figure names could be referred without ".svg" at the ending.
### Details and comments

Some details that should be in this section include:
In #629 , an issue was raised where a figure that was saved with the
name "abcd" couldn't be accessed. This issue is caused by that the
'add_figures()' method in `ExperimentData` class added ".svg"
automatically. As it explicitly written that SVG extension is added if
the file name doesn't have one, we can conclude that all figure names
have ".svg" extension. To not make a major change in the code I added to
the `figure` method in `ExperimentData` class a check for the extension
of the `figure_key`. If it doesn't have ".svg" ending, it adds one
before trying to pull it from the dict of figures.

---------

Co-authored-by: Yael Ben-Haim <[email protected]>

qiskit_experiments/framework/experiment_data.py

@@ -1311,6 +1311,12 @@ def figure(
                 raise ExperimentEntryNotFound(f"Figure {figure_key} not found.")
             figure_key = self._figures.keys()[figure_key]
 
+        # All figures must have '.svg' in their names when added, as the extension is added to the key
+        # name in the `add_figures()` method of this class.
+        if isinstance(figure_key, str):
+            if not figure_key.endswith(".svg"):
+                figure_key += ".svg"
+
         figure_data = self._figures.get(figure_key, None)
         if figure_data is None and self.service:
             figure = self.service.figure(experiment_id=self.experiment_id, figure_name=figure_key)

releasenotes/notes/access_figure_without_extension-5b7438c19e223d6b.yaml

@@ -0,0 +1,4 @@
+---
+upgrade:
+  - |
+    Figures in `ExperimentData` objects can now be accessed without '.svg' extension.

test/database_service/test_db_experiment_data.py

@@ -409,6 +409,8 @@ def test_get_figure(self):
         exp_data = ExperimentData(experiment_type="qiskit_test")
         figure_template = "hello world {}"
         name_template = "figure_{}.svg"
+        name_template_wo_ext = "figure_{}"
+
         for idx in range(3):
             exp_data.add_figures(
                 str.encode(figure_template.format(idx)), figure_names=name_template.format(idx)
@@ -418,6 +420,11 @@ def test_get_figure(self):
         self.assertEqual(expected_figure, exp_data.figure(name_template.format(idx)).figure)
         self.assertEqual(expected_figure, exp_data.figure(idx).figure)
 
+        # Check that figure will be returned without file extension in name
+        expected_figure = str.encode(figure_template.format(idx))
+        self.assertEqual(expected_figure, exp_data.figure(name_template_wo_ext.format(idx)).figure)
+        self.assertEqual(expected_figure, exp_data.figure(idx).figure)
+
         file_name = uuid.uuid4().hex
         self.addCleanup(os.remove, file_name)
         exp_data.figure(idx, file_name)