Adding zoneid and tags

[poddm]

Add tags field and fix zone_ids handling for service offerings

Summary

This PR adds a tags attribute to the service offering resources and fixes a bug where zone_ids was incorrectly overwritten when the CloudStack API returned "all" as the zone ID.

Changes

New tags field

• Added tags as an optional StringAttribute to the common service offering schema
• Added Tags field to serviceOfferingCommonResourceModel
• Added applyTags() helper that sets tags on CreateServiceOfferingParams when non-null
• Affects all three resource types: fixed, constrained, and unconstrained

Fix zone_ids state management

• commonRead and commonUpdate now skip overwriting ZoneIds when the API returns "all" or an empty string — previously this would replace a null/empty plan value with ["all"], causing a perpetual diff
• commonUpdateParams and commonCreateParams: extracted zoneIDs local variable for clarity; no behavioral change

Files Changed

File	Change
service_offering_models.go	Add Tags field
service_offering_schema.go	Add tags schema attribute
service_offering_util.go	Fix zone_ids "all" handling; add applyTags()
service_offering_{fixed,constrained,unconstrained}_resource.go	Wire up new field