Fix action loading in uml

- Refactored actions loading code to eliminate duplicated code.
- Added relevant test case.
- Fixes #588

spring-statemachine-data/jpa/src/test/resources/data15.json

@@ -0,0 +1,39 @@
+[
+	{
+		"@id": "3",
+		"_class": "org.springframework.statemachine.data.jpa.JpaRepositoryAction",
+		"spel": "false"
+	},
+	{
+		"@id": "4",
+		"_class": "org.springframework.statemachine.data.jpa.JpaRepositoryAction",
+		"spel": "false"
+	},
+	{
+		"@id": "5",
+		"_class": "org.springframework.statemachine.data.jpa.JpaRepositoryAction",
+		"spel": "false"
+	},
+	{
+		"@id": "1",
+		"_class": "org.springframework.statemachine.data.jpa.JpaRepositoryState",
+		"initial": true,
+		"state": "S1",
+		"exitActions": ["3"]
+	},
+	{
+		"@id": "2",
+		"_class": "org.springframework.statemachine.data.jpa.JpaRepositoryState",
+		"initial": false,
+		"state": "S2",
+		"entryActions": ["4"],
+		"stateActions": ["5"]
+	},
+	{
+		"_class": "org.springframework.statemachine.data.jpa.JpaRepositoryTransition",
+		"source": "1",
+		"target": "2",
+		"event": "E1",
+		"kind": "EXTERNAL"
+	}
+]