feat(c4) Allow adding attributes.

This allows in example adding hyperlinks to C4 diagrams,
as requested on mingrammer#604.

This also allows further customization for those elements.

diagrams/c4/__init__.py

@@ -58,24 +58,50 @@ def C4Node(name, technology="", description="", type="Container", **kwargs):
 
 
 def Container(name, technology="", description="", **kwargs):
-    return C4Node(name, technology=technology, description=description, type="Container")
+    container_attributes = {
+        "name": name,
+        "technology": technology,
+        "description": description,
+        "type": "Container",
+    }
+    container_attributes.update(kwargs)
+    return C4Node(**container_attributes)
 
 
 def Database(name, technology="", description="", **kwargs):
-    return C4Node(name, technology=technology, description=description, type="Database", shape="cylinder", labelloc="b")
+    database_attributes = {
+        "name": name,
+        "technology": technology,
+        "description": description,
+        "type": "Database",
+        "shape": "cylinder",
+        "labelloc": "b",
+    }
+    database_attributes.update(kwargs)
+    return C4Node(**database_attributes)
 
 
 def System(name, description="", external=False, **kwargs):
-    type = "External System" if external else "System"
-    fillcolor = "gray60" if external else "dodgerblue4"
-    return C4Node(name, description=description, type=type, fillcolor=fillcolor)
+    system_attributes = {
+        "name": name,
+        "description": description,
+        "type": "External System" if external else "System",
+        "fillcolor": "gray60" if external else "dodgerblue4",
+    }
+    system_attributes.update(kwargs)
+    return C4Node(**system_attributes)
 
 
 def Person(name, description="", external=False, **kwargs):
-    type = "External Person" if external else "Person"
-    fillcolor = "gray60" if external else "dodgerblue4"
-    style = "rounded,filled"
-    return C4Node(name, description=description, type=type, fillcolor=fillcolor, style=style)
+    person_attributes = {
+        "name": name,
+        "description": description,
+        "type": "External Person" if external else "Person",
+        "fillcolor": "gray60" if external else "dodgerblue4",
+        "style": "rounded,filled",
+    }
+    person_attributes.update(kwargs)
+    return C4Node(**person_attributes)
 
 
 def SystemBoundary(name, **kwargs):
@@ -90,8 +116,10 @@ def SystemBoundary(name, **kwargs):
 
 
 def Relationship(label="", **kwargs):
-    edge_attribtues = {"style": "dashed", "color": "gray60"}
-    if label:
-        edge_attribtues.update({"label": _format_edge_label(label)})
-    edge_attribtues.update(kwargs)
-    return Edge(**edge_attribtues)
+    edge_attributes = {
+        "style": "dashed",
+        "color": "gray60",
+        "label": _format_edge_label(label) if label else "",
+    }
+    edge_attributes.update(kwargs)
+    return Edge(**edge_attributes)