Adding setters or making them public in ActionRequests

[pickypg]

MoreLikeThisRequest, AnalyzeRequest, and DeleteIndexTemplateRequest (and associated builders) all prevented some fields from being set outside their constructor. This makes those fields publically settable, which helps to simplify usage in other languages like Groovy.

Closes #8122

[colings86]

Although helps to simplify things in languages like groovy I am concerned about the impact it has on the Java API. I would assume that the reason these fields are explicitly prevented from being set outside the constructor is that they are required parameters (e.g. you must specify the name of the template you want to delete). By making them optional in the Java API we increase the risk that someone will accidentally not set it causing a headache for the user. Furthermore, since this fields have always been guaranteed to be set I would be wary of unknown side-effects if the request did get made with those fields set to null. The code may not guard against these fields being null, at best this would result in a NPE, at worst the null could be interpreted as all and have serious side-effects.

[pickypg]

@colings86 I think that they were overlooked because it was already added to the Validation API. Honestly, it should just fail at the constructor rather than being a surprise later if we don't change it.

Except MoreLikeThisRequest, which apparently does not use the Validation API and I suspect that it should.

[javanna]

I think all of the requests should ideally do validation using the validate method. If MoreLikeThisRequest doesn't we should fix it. That said some of them can enforce required arguments by making them required in their constructor. But I am not against adding setters too for them, as long as validate method works properly, for consistency reasons. I tend to be against adding empty constructors though to those requests, especially if using the @Nullable annotation for required fields. Does this make sense?

[s1monw]

@javanna can you take care of this and work with @pickypg towards closing / merging, thanks!

[javanna]

Do you have time to address my comments @pickypg ? Let me know if you have any question.

[javanna]

I pushed a fix for this: note that the more like this api is gone in master, thus no need to modify anything there. AnalyzeRequest already had text setter after #3023 was resolved. I added the name setter to DeleteIndexTemplateRequest. Also made public default constructors for AnalyzeRequest and DeleteIndexTemplateRequest, given that through their corresponding builder it is already possible to create a request without required parameters, the validate method will throw error though.