Include metadata as part of create_vm and create_disk

proposals/include-metadata.md

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+- State: discussing
+- Start date: ?
+- End date: ?
+- Docs: ?
+
+# Summary
+
+CPI should pass metadata information as part of create_vm, create_disk, create_snapshot call
+
+# Motivation
+
+To be able to use this metadata information e.g deployment_name/instance_group name during vm_creation.
+VM CID can be prefixed with instance_group name so that it is easy to identify VM in vCenter.
+Created disk could also be organized using this metadata information
+
+# Details
+
+Metadata will include basic information about director, deployment and instance_group. All the tags that is being sent as part of set_vm_metadata call right now.
+E.g
+
+```
+{
+  director_name: "production-director",
+  director_uuid: "abcd-2134-5678"
+  deployment_name: "kafka",
+  instance_group: "my_instance_group",
+  }
+
+```
+
+create_vm interface will now be:
+
+```create_vm(agent_id, stemcell_cid, cloud_properties, network_settings, disks, env, metadata)```
+
+create_disk interface will now be:
+
+```create_disk(size, cloud_properties, vm_locality, metadata)```
+
+Information provided in metadata is right now passed as part of groups array inside env hash. CPI is not supposed to 
+rely on this information. Adding new argument metadata will make this data more reliable and useful for various IAAS.
+
+There have been request for this from different IAAS as well. See Issue #[62](https://github.com/cloudfoundry/bosh-aws-cpi-release/issues/62), Issue #[1163](https://github.com/cloudfoundry/bosh/issues/1163) 
+
+# Drawbacks
+
+Change to CPI contract
+
+# Unresolved questions
+
+How should set_vm_metadata and set_disk_metadat methods be updated?
+
+As suggested set_vm_metadata and set_disk_metadata could send metadata keys hich can change later after the initial create vm/disk/snapshot call.