Added getters for JsonPatch and Operations

[GavinF17]

Hoping this gets picked up & released due to recent activity by @Capstan :)

• Added JsonPatch.getOperations()
• Added field getters for operations
  • DualPathOperation.getFrom()
  • JsonPatchOperation.getOp() and JsonPatchOperation.getPath()
  • PathValueOperation.getValue()

Personal use case is needing to determine which class to patch when using subtypes, and the type info being held in a field which may be modified by a replace operation.

Solves #33
Supercedes #45

[Spellmaker]

I'm also highly interested in this PR getting merged, getters would be really useful for examining the operations (in my use-case: checking for certain paths to discourage changes to some part of the json document)

[serac]

My use case is similar to @Spellmaker but notably different. We have JSON models that map to database models where only some fields are mutable via our REST API. We need to be able to examine a patch request in order to validate that the JSON paths are mutable according to business policy. While we could do this with raw JSON and then parse it into a JsonPatch object after validation, it would be far more convenient to work with the parsed version where the operation and path are easily accessible on a JsonPatch object.

As far as this PR, it seems innocuous as operations is final and wrapped in an immutable collection, so there's no risk of clients mutating the internal state by exposing it via a getter. I hope you'll consider this enhancement.

[Capstan]

Looks good overall.

[Capstan]

Should this protectively copy the string?

[GavinF17]

I wouldn't have thought this is necessary as String is immutable, if I'm not thinking of something can you please explain?

[Capstan]

Ah, you're right.

[GavinF17]

Looks good overall.

Thanks for the feedback, addressed all comments with one outstanding

[elalex2021]

I am using v.13 (https://mvnrepository.com/artifact/com.github.java-json-tools/json-patch/1.13), but still not able to use method getOperations().

[ceenlrnjim]

We are also interested in having the getOperations accessor and see that it isn't in 1.13 - are there plans for another release that will pick up this change?