update postgres test container

- update README.md
- update PostgresContainer
  - add TestExecutionListeners
  - remove ExtendWith
- update PostgresInitializer
  - cleanup
  - use properties for script and container
  - add afterTestClass
  - add beforeTestClass
  - extend TestExecutionListener
- remove PostgresExtension
- add debug logging to PostgresExecutor
- add ContainerUtils
- add dependencies
- extract function from PostgresExtension to PostgresExecutor

src/main/kotlin/ltd/hlaeja/test/util/ContainerUtil.kt

@@ -0,0 +1,26 @@
+package ltd.hlaeja.test.util
+
+import org.springframework.context.ConfigurableApplicationContext
+import org.springframework.core.io.ClassPathResource
+import org.springframework.test.context.TestContext
+
+fun ConfigurableApplicationContext.getProperty(
+    property: String,
+): String? = this.environment.getProperty(property)
+
+fun ConfigurableApplicationContext.getProperty(
+    property: String,
+    default: String,
+): String = this.environment.getProperty(property, default)
+
+fun TestContext.getProperty(
+    property: String,
+): String? = this.applicationContext.environment.getProperty(property)
+
+fun String.isResourceFile(): ClassPathResource? {
+    val resource = ClassPathResource(this)
+    return when {
+        resource.exists() && resource.isReadable -> resource
+        else -> null
+    }
+}