Only report bug warning in precise conditions.

[wu-sheng]

• If this pull request closes/resolves/fixes an existing issue, replace the issue number. Closes #.
• Update the CHANGES log.

User will see the [Bug warning] in 2 typical cases

1. If the template exists and index deleted, or in reverse. In this case, this isn't the bug report we expected.
2. OAP shut down over a day and latest index doesn't exist for sure. In this case, we just need to return false, and create method will fix this.

[kezhenxu94]

If this is the only condition, I think a basic test should cover it, this is a very basic logic and should be discovered at test phase, not runtime

        assertThat(templateClient.exists(name)).isTrue();

skywalking/oap-server/server-library/library-elasticsearch-client/src/test/java/org/apache/skywalking/library/elasticsearch/ITElasticSearchTest.java

Lines 102 to 107 in 73b6c67

	assertThat(templateClient.get(name))
	.isPresent()
	.map(IndexTemplate::getMappings)
	.map(Mappings::getProperties)
	.hasValue(mappings.getProperties());
	}

[wu-sheng]

I was proposing this due to we can't test all server versions, and as we are not official, we can't tell when breaking change happens.
This exception codes should never be executed.

[wu-sheng]

The current conditions checking could fail in daily used, it is not a bug, and we have to suffer endless question and bug report on GitHub.

[kezhenxu94]

The current conditions checking could fail in daily used, it is not a bug, and we have to suffer endless question and bug report on GitHub.

I don't mean to keep the current conditions, I mean if the condition is to be if ((templateExists && !template.isPresent()) || (!templateExists && template.isPresent())), then this is a very basic function that we should test in the perspective of ES client.

I was proposing this due to we can't test all server versions, and as we are not official, we can't tell when breaking change happens.

The supported versions are fixed and the codes won't run on un-tested versions.

skywalking/oap-server/server-library/library-elasticsearch-client/src/main/java/org/apache/skywalking/library/elasticsearch/ElasticSearchVersion.java

Line 67 in 73b6c67

throw new UnsupportedOperationException("Unsupported version: " + this);

We will manually test a new ES version, and add it into our supported list, otherwise if users run on a future ES server for example 8.2, the OAP won't even start

[kezhenxu94]

It's good to me to keep the new condition, but please also add a test to

skywalking/oap-server/server-library/library-elasticsearch-client/src/test/java/org/apache/skywalking/library/elasticsearch/ITElasticSearchTest.java

Lines 102 to 107 in 73b6c67

	assertThat(templateClient.get(name))
	.isPresent()
	.map(IndexTemplate::getMappings)
	.map(Mappings::getProperties)
	.hasValue(mappings.getProperties());
	}

        assertThat(templateClient.exists(name)).isTrue();

[wu-sheng]

The supported versions are fixed and the codes won't run on un-tested versions.

I know we have {"6.3.2"}, {"7.4.2"}, {"7.8.0"}, {"7.10.2"}, but who knows one day, something breaks unexpected, such as we never knew in the 7.x there are different cases.

It's good to me to keep the new condition, but please also add a test to

Added check for template existing check.