FL-952 feat: add UserFriendsCreated event and extend CustomerUpdated with privacy fields

Summary

SDK extension for FL-952 (Public/Private Profile Visibility).

Adds one new event and extends one existing event payload to support:

• Auto-Approve on PUBLIC profile (single friend)
• Mass Auto-Accept on PRIVATE → PUBLIC transition (batch of N)
• Push storm mitigation via single consolidated event
• CMS-owned data (postsCount, whoCanViewPosts) propagation to FMS without HTTP coupling

See ADR-006 for the full design rationale and migration strategy.

Changes

New event: fms.UserFriendsCreated

type UserFriendsCreated struct {
    UserID         uuid.UUID   `json:"userId" validate:"required"`
    NewFriendsIDs  []uuid.UUID `json:"newFriendsIds" validate:"required,min=1,dive,required"`
    IsAutoAccepted bool        `json:"isAutoAccepted"`
}

Topic: fms.user_friends.created

One event covers three cases:

• Manual accept (Phase 2+): len=1, IsAutoAccepted=false
• Auto-Approve PUBLIC: len=1, IsAutoAccepted=true
• Mass Auto-Accept: len=N, IsAutoAccepted=true

Deprecated: fms.UserFriendCreated

Marked // Deprecated: use UserFriendsCreated. Kept in SDK during Phase 1 (manual-accept publish path); removal planned in a follow-up task.

Extended: cps.CustomerUpdated

+4 optional fields (all omitempty + validated):

• ProfileVisibility (PUBLIC | PRIVATE) — owned by UPM
• PostsCount (*int64) — owned by CMS, propagated for FMS profile response
• WhoCanViewPosts (ALL | FRIENDS_OF_FRIENDS | FRIENDS | ONLY_ME) — owned by CMS, propagated for FMS BR-14 check
• WhoCanViewOrdersPosts — same as above

New types in cps package

• ProfileVisibility enum
• PostVisibility enum

Migration strategy

Phase 1 (this MR): both UserFriendCreated and UserFriendsCreated live in parallel. Phase 2 (separate task): migrate manual-accept publishers to new event. Phase 3 (separate task): remove deprecated UserFriendCreated.

Test plan

• go build ./... — clean
• go vet ./... — clean
• gofmt -l . — clean
• go test ./... — all packages pass
• New tests: 8 cases for UserFriendsCreated (3 success use cases, 3 failure cases, naming, JSON roundtrip)
• New tests: 6 cases for CustomerUpdated privacy fields (success PUBLIC/PRIVATE/omitted, fail invalid enum, all PostVisibility values loop)

Related

• Jira: FL-952
• Design: ADR-006 — SDK extension
• [Backend] Бриф §5 — SDK events section