added logstash model for converter

[asifsmohammed]

Description

Added sub-project data-prepper-logstash-configuration and Logstash model to store the information from Logstash configuration files.

Issues Resolved

Resolve #446

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[laneholloway]

Please rename the classes to be more explicit about what is being modeled and cleanup the build.gradle file for the data-prepper-logstash-configuration

[laneholloway]

Just add the @since 1.2 on the enum class and I'll approve.

[cmanning09]

Are we allowing these objects to be multated? I would recommend we avoid mutation as it is harder to debug. If we can remove the setter functions, please make the attributeValue and attribute name as final.

If we need these setters, plese make the method parameter to the method final. Same is true for the other model objects.

[asifsmohammed]

Yeah, they should be immutable. Will update the model

[treddeni-amazon]

Are we not going to use the builder pattern for creating our model objects?

[cmanning09]

Let's just call this Builder. Otherwise, we will invoke the builder like so: LogstashAttribute = new LogstashAttribute.LogstashAttributeBuilder().build();

I would also recommend creating a public static method to get the builder so we can avoid having to use new:

public static Builder builder() {
    return new Builder();
}

Then we could just invoke the builder like so:

final LogstashAttribute logstashAttribute = LogstashAttribute.builder()
        .withAttributeValue(attributeValue)
        .withAttributeName("foobar")
        .build();

[laneholloway]

@cmanning09 great advice.

[cmanning09]

Do we have any requirements on these values? Can they be null or do we need to enforce non-null?

The same question applies to the other models.

[asifsmohammed]

Technically they shouldn't be null, but we might have some section in configuration left empty and we have to use default values.
For example, it can be like
http{
}

But I think we can still add a validate method to enforce non-null

[laneholloway]

@asifsmohammed can you go ahead and add the validation for non-nulls?, please.

[dlvenable]

In the case of:

http {
}

You should have an empty array of LogstashAttribute in the LogstashPlugin. I'm unsure if the attributeValue can be null or not, but the attributeName should not be null.

[asifsmohammed]

I've added the non-null validation.

[dlvenable]

One additional comment:

We know that we want to move our packages to org.opensearch.dataprepper from com.amazon.dataprepper per #344. Most of that work will need to wait until v2.0 so as to not break any existing class.

However, this is a brand new sub-module within Data Prepper. Should we use this new package in here starting now? Or do we just want to change them all in v2.0?

[laneholloway]

This is new work, let's go ahead and start the migration to org.opensearch.dataprepper with this. @asifsmohammed, sorry for making this a longer review than normal, but it's a good place to start doing the work.