Polish ObservationConvention Configuration

Change to setObservationConvention so that it reads more clearly
when used, for example `authenticationManager.setObservationConvention`
is clearer than `authenticationManager.setConvention`.

Change unit test names to follow team conventions.

Issue gh-12534

core/src/test/java/org/springframework/security/authentication/ObservationAuthenticationManagerTests.java

@@ -94,8 +94,9 @@ public class ObservationAuthenticationManagerTests {
 	}
 
 	@Test
-	void conventionSetterThrowsWhenNull() {
-		assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> this.tested.setConvention(null));
+	void setObservationConventionWhenNullThenException() {
+		assertThatExceptionOfType(IllegalArgumentException.class)
+				.isThrownBy(() -> this.tested.setObservationConvention(null));
 	}
 
 }

core/src/test/java/org/springframework/security/authentication/ObservationReactiveAuthenticationManagerTests.java

@@ -97,8 +97,9 @@ public class ObservationReactiveAuthenticationManagerTests {
 	}
 
 	@Test
-	void conventionSetterThrowsWhenNull() {
-		assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> this.tested.setConvention(null));
+	void setObservationConventionWhenNullThenException() {
+		assertThatExceptionOfType(IllegalArgumentException.class)
+				.isThrownBy(() -> this.tested.setObservationConvention(null));
 	}
 
 }

core/src/test/java/org/springframework/security/authorization/ObservationAuthorizationManagerTests.java

@@ -119,8 +119,9 @@ public class ObservationAuthorizationManagerTests {
 	}
 
 	@Test
-	void conventionSetterThrowsWhenNull() {
-		assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> this.tested.setConvention(null));
+	void setObservationConventionWhenNullThenException() {
+		assertThatExceptionOfType(IllegalArgumentException.class)
+				.isThrownBy(() -> this.tested.setObservationConvention(null));
 	}
 
 }

core/src/test/java/org/springframework/security/authorization/ObservationReactiveAuthorizationManagerTests.java

@@ -118,8 +118,9 @@ public class ObservationReactiveAuthorizationManagerTests {
 	}
 
 	@Test
-	void conventionSetterThrowsWhenNull() {
-		assertThatExceptionOfType(IllegalArgumentException.class).isThrownBy(() -> this.tested.setConvention(null));
+	void setObservationConventionWhenNullThenException() {
+		assertThatExceptionOfType(IllegalArgumentException.class)
+				.isThrownBy(() -> this.tested.setObservationConvention(null));
 	}
 
 }