fix: remove rules types package import from migration #049 (#12998)

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#### Description

Migration package ideally should have have things from types package
imported. Given that rules v1->v2 will (most probably) update/remove
some of the types, such as removing `PreferredChannels` from
`PostableRule`, better not to have this type imported in migrations
package.

<!--Reference issues using `Closes #issue-number` to enable automatic
closure on merge. -->
#### Issues closed by this PR

Part of https://github.com/SigNoz/pulse-pod/issues/225

pkg/sqlmigration/049_add_route_policy.go

@@ -13,7 +13,6 @@ import (
 	"github.com/SigNoz/signoz/pkg/sqlschema"
 	"github.com/SigNoz/signoz/pkg/sqlstore"
 	"github.com/SigNoz/signoz/pkg/types"
-	"github.com/SigNoz/signoz/pkg/types/ruletypes"
 	"github.com/SigNoz/signoz/pkg/valuer"
 	"github.com/uptrace/bun"
 	"github.com/uptrace/bun/migrate"
@@ -50,6 +49,11 @@ type rule struct {
 	OrgID   string `bun:"org_id,type:text"`
 }
 
+type routePolicyRuleData struct {
+	PreferredChannels []string          `json:"preferredChannels"`
+	Labels            map[string]string `json:"labels"`
+}
+
 type addRoutePolicies struct {
 	sqlstore  sqlstore.SQLStore
 	sqlschema sqlschema.SQLSchema
@@ -187,20 +191,20 @@ func (migration *addRoutePolicies) migrateRulesToRoutePolicies(ctx context.Conte
 func (migration *addRoutePolicies) convertRulesToRoutes(rules []*rule, channelsByOrg map[string][]string) ([]*expressionRoute, error) {
 	var routes []*expressionRoute
 	for _, r := range rules {
-		var gettableRule ruletypes.GettableRule
-		if err := json.Unmarshal([]byte(r.Data), &gettableRule); err != nil {
+		var ruleData routePolicyRuleData
+		if err := json.Unmarshal([]byte(r.Data), &ruleData); err != nil {
 			return nil, errors.NewInternalf(errors.CodeInternal, "failed to unmarshal rule data for rule ID %s: %v", r.ID, err)
 		}
 
-		if len(gettableRule.PreferredChannels) == 0 {
+		if len(ruleData.PreferredChannels) == 0 {
 			channels, exists := channelsByOrg[r.OrgID]
 			if !exists || len(channels) == 0 {
 				continue
 			}
-			gettableRule.PreferredChannels = channels
+			ruleData.PreferredChannels = channels
 		}
 		severity := "critical"
-		if v, ok := gettableRule.Labels["severity"]; ok {
+		if v, ok := ruleData.Labels["severity"]; ok {
 			severity = v
 		}
 		expression := fmt.Sprintf(`%s == "%s" && %s == "%s"`, "threshold.name", severity, "ruleId", r.ID.String())
@@ -218,7 +222,7 @@ func (migration *addRoutePolicies) convertRulesToRoutes(rules []*rule, channelsB
 			},
 			Expression:     expression,
 			ExpressionKind: "rule",
-			Channels:       gettableRule.PreferredChannels,
+			Channels:       ruleData.PreferredChannels,
 			Name:           r.ID.StringValue(),
 			Enabled:        true,
 			OrgID:          r.OrgID,