Upgrade to terraform-plugin-sdk/v2 and add new resources/data sources

[aamirk-splunk]

Summary

This PR modernizes the VictorOps Terraform provider by upgrading to terraform-plugin-sdk/v2 and adding new resources and data sources.

SDK Upgrade

• Previous: terraform-plugin-sdk v1.8
• Current: terraform-plugin-sdk/v2

Key Changes

• All resource functions now use Context variants (CreateContext, ReadContext, UpdateContext, DeleteContext)
• Return types changed from error to diag.Diagnostics for richer error reporting
• Import support added via schema.ResourceImporter

New Resources

Resource	Description
victorops_scheduled_override	Manage scheduled overrides on escalation policies
victorops_maintenance_mode	Manage maintenance mode windows
victorops_alert_rule	Manage alert rules on routing keys

New Data Sources

Data Source	Description
victorops_user	Look up a single user by username
victorops_users	List all users in the organization
victorops_team	Look up a single team by slug
victorops_teams	List all teams in the organization
victorops_escalation_policy	Look up a single escalation policy by ID
victorops_escalation_policies	List all escalation policies (optionally filtered by team)
victorops_routing_keys	List all routing keys
victorops_rotations	List rotations for a specific team
victorops_on_call	Get current on-call schedule

Import Support

Added import support for all applicable resources:

Resource	Import ID Format
victorops_team	{team_slug}
victorops_user	{username}
victorops_contact	{username}/{type}/{contact_id}
victorops_escalation_policy	{policy_id}
victorops_routing_key	{routing_key_name}
victorops_scheduled_override	{policy_slug}/{override_id}
victorops_maintenance_mode	{instance_id}
victorops_alert_rule	{routing_key}/{rule_id}

Breaking Changes

• Requires Terraform 0.12+
• Uses terraform-plugin-sdk/v2

Version Compatibility

Component	Minimum Version
Go	1.22+
Terraform	0.12+
terraform-plugin-sdk	v2.0+