Issue-6642 Add http.send request attribute to ignore headers for caching key

[rudrakhp]

Why the changes in this PR are needed?

Need to support exclusion of certain headers from http.send query cache key.

What are the changes in this PR?

• A new attribute cache_ignored_headers in the http.send built in request object. Enables policy authors to define an exclusion list for headers to ignore while caching.
• Modify key used by the HTTP request executor when building the cache key.
• Unit tests for these changes.

Notes to assist PR review:

• Note that if request attribute cache_ignored_headers changes but does not affect the final computed cache key, the results are still served from cache. This attribute is always excluded from the cache key.
• If there is a change in the exclusion list that leads to change in the cache key (addition/removal of a header), a new cache key is generated which leads to a cache miss.

Further comments:

Resolves #6642

[rudrakhp]

Thanks for working on this. Here we are excluding certain headers from the key calculation. Is there a reason for that level of granularity? Why not exclude certain request object params themselves from the key calculation?

I would have to explore if there is any straight forward way to delete a value by path reference in the Request ast.Object, since we might require that to ignore any generic request attribute from the cache key. Let me get back to you on this next week. Meanwhile please do share if you have any pointers. Thanks!

[ashutosh-narkar]

@rudrakhp just checking to see if you got a chance to explore the option of excluding certain request object params.

[rudrakhp]

@ashutosh-narkar was out last week, will raise an updated PR this week.

[stale[bot]]

This pull request has been automatically marked as stale because it has not had any activity in the last 30 days.

[ashutosh-narkar]

@rudrakhp this would be a good one to get in the next release. Let us know if you need any help. Thanks.

[rudrakhp]

@ashutosh-narkar I just realised that request object was a pointer and it was getting modified as we modify the key, the downstream request will also not get these ignored headers. I have made a couple of new changes to address that, please do review. Thanks for the comments!

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