add feature flag for search relevance workbench

[fen-qin]

Description

Add a feature flag to by defaulted enable search relevance workbench. When dashboards read the cluster settings, it can do the access control to opt-in/opt-out user experience between old version and new version.

• feature flag = true by defaulted
• if customers choose to opt-out SRW, feature flag = false
  • feature flag will block all rest APIs calls

GET localhost:9200/_cluster/settings?include_defaults=true
...
{
    "plugins": {
        ...
        "search_relevance": {
		"workbench_enabled": "true"     // defaulted value
	}
}

• any API calls will get the 403 response

Search Relevance Workbench is disabled

Issues Resolved

#33
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[epugh]

LGTM.

[martin-gaievski]

I think flag should be "enabled" by default and user needs to opt-out in case they don't want SRW
@heemin32

[fen-qin]

@martin-gaievski @heemin32
here is the feature flag change for frontend - o19s/dashboards-search-relevance#53

• feature flag by defaulted is false -> old user experience

• and currently, I enabled DYNAMIC, so after update cluster settings to enable feature flag -> new user experience

Can you check if my understanding here is correct ? My action items on this task:

• reverse, it should be by-defaulted as true, then customer choose to opt-out ?
• when to remove the DYNAMIC. I keep the DYNAMIC here to make it easier for all of us to validate the changes. Otherwise, it will be old experience

[heemin32]

reverse, it should be by-defaulted as true, then customer choose to opt-out ?

Yes

when to remove the DYNAMIC. I keep the DYNAMIC here to make it easier for all of us to validate the changes. Otherwise, it will be old experience

We should keep it as dynamic.

[fen-qin]

reverse the feature flag. By defaulted, customers are opt-in the SWR. Then they can choose to opt-out SWR to use old experience.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (e7c98c9) to head (bf3096d).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##               main   #34       +/-   ##
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- Coverage     14.48%     0   -14.49%     
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  Files           107     0      -107     
  Lines          3313     0     -3313     
  Branches        236     0      -236     
==========================================
- Hits            480     0      -480     
+ Misses         2808     0     -2808     
+ Partials         25     0       -25     

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