feat: outline around dots of scatterplot (#785)

### Summary of Changes

Draw a white outline around the dots of a scatterplot to easily view
overlapping dots.

---------

Co-authored-by: megalinter-bot <129584137+megalinter-bot@users.noreply.github.com>

src/safeds/data/tabular/plotting/_table_plotter.py

@@ -5,6 +5,7 @@
 
 from safeds._utils import _figure_to_image
 from safeds._validation import _check_columns_exist
+from safeds._validation._check_columns_are_numeric import _check_columns_are_numeric
 from safeds.exceptions import NonNumericColumnError
 
 if TYPE_CHECKING:
@@ -322,19 +323,17 @@ def scatter_plot(self, x_name: str, y_name: str) -> Image:
         >>> image = table.plot.scatter_plot("a", "b")
         """
         _check_columns_exist(self._table, [x_name, y_name])
-
-        # TODO: pass list of columns names + extract validation
-        if not self._table.get_column(x_name).is_numeric:
-            raise NonNumericColumnError(x_name)
-        if not self._table.get_column(y_name).is_numeric:
-            raise NonNumericColumnError(y_name)
+        _check_columns_are_numeric(self._table, [x_name, y_name])
 
         import matplotlib.pyplot as plt
 
         fig, ax = plt.subplots()
         ax.scatter(
             x=self._table.get_column(x_name)._series,
             y=self._table.get_column(y_name)._series,
+            s=64,  # marker size
+            linewidth=1,
+            edgecolor="white",
         )
         ax.set(
             xlabel=x_name,

tests/safeds/data/tabular/containers/_table/test_plot_scatterplot.py

@@ -1,12 +1,31 @@
 import pytest
 from safeds.data.tabular.containers import Table
-from safeds.exceptions import ColumnNotFoundError
+from safeds.exceptions import ColumnNotFoundError, ColumnTypeError
 from syrupy import SnapshotAssertion
 
 
-def test_should_match_snapshot(snapshot_png_image: SnapshotAssertion) -> None:
-    table = Table({"A": [1, 2, 3], "B": [2, 4, 7]})
-    scatterplot = table.plot.scatter_plot("A", "B")
+@pytest.mark.parametrize(
+    ("table", "x_name", "y_name"),
+    [
+        (Table({"A": [1, 2, 3], "B": [2, 4, 7]}), "A", "B"),
+        (
+            Table(
+                {
+                    "A": [1, 0.99, 0.99, 2],
+                    "B": [1, 0.99, 1.01, 2],
+                },
+            ),
+            "A",
+            "B",
+        ),
+    ],
+    ids=[
+        "functional",
+        "overlapping",
+    ],
+)
+def test_should_match_snapshot(table: Table, x_name: str, y_name: str, snapshot_png_image: SnapshotAssertion) -> None:
+    scatterplot = table.plot.scatter_plot(x_name, y_name)
     assert scatterplot == snapshot_png_image
 
 
@@ -23,3 +42,15 @@ def test_should_match_snapshot(snapshot_png_image: SnapshotAssertion) -> None:
 def test_should_raise_if_column_does_not_exist(table: Table, col1: str, col2: str) -> None:
     with pytest.raises(ColumnNotFoundError):
         table.plot.scatter_plot(col1, col2)
+
+
+@pytest.mark.parametrize(
+    ("table", "x_name", "y_name"),
+    [
+        (Table({"A": ["a", "b", "c"], "B": [2, 4, 7]}), "A", "B"),
+        (Table({"A": [1, 2, 3], "B": ["a", "b", "c"]}), "A", "B"),
+    ],
+)
+def test_should_raise_if_columns_are_not_numeric(table: Table, x_name: str, y_name: str) -> None:
+    with pytest.raises(ColumnTypeError):
+        table.plot.scatter_plot(x_name, y_name)