[Proposal] Rename verb-first fields in SDK action structs to noun-first naming

[renuka-fernando]

Summary

• Rename verb-prefixed fields in UpstreamRequestModifications, UpstreamResponseModifications, and ImmediateResponse to use noun-first naming (e.g., SetHeaders -> HeadersToSet)
• Remove AppendHeaders (will not be supported)
• Aligns all struct fields with Go convention: struct fields are data (nouns), methods are behavior (verbs)
• Breaking change to the policy SDK public API in sdk/gateway/policy/v1alpha/action.go

Motivation

• The action structs mix two naming styles: verb-first (SetHeaders, RemoveHeaders, AppendHeaders) and noun-first (Body, Path, Method, AnalyticsMetadata), creating inconsistency within the same struct
• Verb-prefixed field names like mods.SetHeaders read like function calls rather than data access, which is confusing when used alongside genuinely noun-based fields
• Go stdlib follows noun-based naming for struct fields consistently (http.Request.Header, http.Request.Body, http.Request.Method)
• Noun-first naming groups related fields together in IDE autocomplete (all Headers* fields cluster, all QueryParameters* fields cluster)

Proposal

• Rename verb-first fields to noun-first across all three affected structs
• Keep fields that are already noun-based (Body, Path, Method, StatusCode, Headers, AnalyticsMetadata, DynamicMetadata) unchanged
• See current struct definitions (v0.9.0) for existing field names

Proposed Changes

Current Name	New Name	Notes
SetHeaders	HeadersToSet	Rename
RemoveHeaders	HeadersToRemove	Rename
AppendHeaders	—	Remove (not going to be supported)
AddQueryParameters	QueryParametersToAdd	Rename
RemoveQueryParameters	QueryParametersToRemove	Rename
DropHeadersFromAnalytics	TBD (see below)	Rename
Body, Path, Method, StatusCode, Headers, AnalyticsMetadata, DynamicMetadata	No change	Already noun-based

Options for DropHeadersFromAnalytics

#	Option	Style	Example Usage
1	AnalyticsHeaderExclusions	Pure noun	mods.AnalyticsHeaderExclusions = ...
2	HeadersToExcludeFromAnalytics	Noun + ToVerb (consistent with others)	mods.HeadersToExcludeFromAnalytics = ...
3	HeadersToDropFromAnalytics	Noun + ToVerb (keeps "drop")	mods.HeadersToDropFromAnalytics = ...
4	ExcludedAnalyticsHeaders	Adjective + noun	mods.ExcludedAnalyticsHeaders = ...

References

• Go stdlib http.Request - noun-based field naming example
• sdk/gateway/policy/v1alpha/action.go - source file with current definitions