[bugfix] Update interaction policies of freshly dereffed statuses if different from last deref (#4474)

# Description

> If this is a code change, please include a summary of what you've coded, and link to the issue(s) it closes/implements.
>
> If this is a documentation change, please briefly describe what you've changed and why.

This pull request adds a check to see whether interaction policy on a refreshed status is different from the interaction policy set on that status before, and updates the status with the new policy if it's changed.

Should fix a pesky issue where folks on v0.19.2 and above still can't interact with statuses they dereferenced before updating.

## Checklist

Please put an x inside each checkbox to indicate that you've read and followed it: `[ ]` -> `[x]`

If this is a documentation change, only the first checkbox must be filled (you can delete the others if you want).

- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [x] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [x] I/we have commented the added code, particularly in hard-to-understand areas.
- [ ] I/we have made any necessary changes to documentation.
- [ ] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
- [x] I/we have run `go fmt ./...` and `golangci-lint run`.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4474
Reviewed-by: kim <gruf@noreply.codeberg.org>
Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Co-committed-by: tobi <tobi.smethurst@protonmail.com>

internal/federation/dereferencing/status.go

@@ -608,6 +608,9 @@ func (d *Dereferencer) enrichStatus(
 		return nil, nil, gtserror.Newf("error populating emojis for status %s: %w", uri, err)
 	}
 
+	// Check if interaction policy has changed between status and latestStatus.
+	interactionPolicyChanged := status.InteractionPolicy.DifferentFrom(latestStatus.InteractionPolicy)
+
 	if isNew {
 		// Simplest case, insert this new remote status into the database.
 		if err := d.state.DB.PutStatus(ctx, latestStatus); err != nil {
@@ -625,6 +628,7 @@ func (d *Dereferencer) enrichStatus(
 			tagsChanged,
 			mediaChanged,
 			emojiChanged,
+			interactionPolicyChanged,
 		)
 		if err != nil {
 			return nil, nil, gtserror.Newf("error handling edit for status %s: %w", uri, err)
@@ -1057,6 +1061,7 @@ func (d *Dereferencer) handleStatusEdit(
 	tagsChanged bool,
 	mediaChanged bool,
 	emojiChanged bool,
+	interactionPolicyChanged bool,
 ) (
 	cols []string,
 	err error,
@@ -1141,6 +1146,15 @@ func (d *Dereferencer) handleStatusEdit(
 		// been previously populated properly.
 	}
 
+	if interactionPolicyChanged {
+		// Interaction policy changed.
+		cols = append(cols, "interaction_policy")
+
+		// Int pol changed doesn't necessarily
+		// indicate an edit, it may just not have
+		// been previously populated properly.
+	}
+
 	if edited {
 		// Get previous-most-recent modified time,
 		// which will be this edit's creation time.

internal/gtsmodel/interactionpolicy.go

@@ -17,6 +17,8 @@
 
 package gtsmodel
 
+import "slices"
+
 // A policy URI is GoToSocial's internal representation of
 // one ActivityPub URI for an Actor or a Collection of Actors,
 // specific to the domain of enforcing interaction policies.
@@ -232,6 +234,39 @@ type PolicyRules struct {
 	ManualApproval PolicyValues `json:"WithApproval,omitempty"`
 }
 
+// DifferentFrom returns true if pr1 and pr2
+// are not equal in terms of nilness or content.
+func (pr1 *PolicyRules) DifferentFrom(pr2 *PolicyRules) bool {
+	// If one PolicyRules is nil and
+	// the other isn't, they're different.
+	if pr1 == nil && pr2 != nil ||
+		pr1 != nil && pr2 == nil {
+		return true
+	}
+
+	// Check if AutomaticApproval
+	// differs between the two.
+	if slices.Compare(
+		pr1.AutomaticApproval,
+		pr2.AutomaticApproval,
+	) != 0 {
+		return true
+	}
+
+	// Check if ManualApproval
+	// differs between the two.
+	if slices.Compare(
+		pr1.ManualApproval,
+		pr2.ManualApproval,
+	) != 0 {
+		return true
+	}
+
+	// They're the
+	// same picture.
+	return false
+}
+
 // Returns the default interaction policy
 // for the given visibility level.
 func DefaultInteractionPolicyFor(v Visibility) *InteractionPolicy {
@@ -422,3 +457,41 @@ func DefaultInteractionPolicyDirect() *InteractionPolicy {
 	*c = *defaultPolicyDirect
 	return c
 }
+
+// DifferentFrom returns true if p1 and p2 are different.
+func (ip1 *InteractionPolicy) DifferentFrom(ip2 *InteractionPolicy) bool {
+	// If one policy is null and the
+	// other isn't, they're different.
+	if ip1 == nil && ip2 != nil ||
+		ip1 != nil && ip2 == nil {
+		return true
+	}
+
+	// If they're both nil we don't
+	// need to check anything else.
+	if ip1 == nil && ip2 == nil {
+		return false
+	}
+
+	// If CanLike differs from one policy
+	// to the next, they're different.
+	if ip1.CanLike.DifferentFrom(ip2.CanLike) {
+		return true
+	}
+
+	// If CanReply differs from one policy
+	// to the next, they're different.
+	if ip1.CanReply.DifferentFrom(ip2.CanReply) {
+		return true
+	}
+
+	// If CanAnnounce differs from one policy
+	// to the next, they're different.
+	if ip1.CanAnnounce.DifferentFrom(ip2.CanAnnounce) {
+		return true
+	}
+
+	// Looks the
+	// same chief.
+	return false
+}