create-template: support --user-data and --volumes

[ivyleavedtoadflax]

Feature request

remote ami create-template currently only supports --ami, --instance-type, and --key-name. Two common launch template fields are missing:

--user-data

Allow passing a cloud-init script when creating or versioning a template:

remote ami create-template my-template \
  --ami ami-xxx --instance-type t3.micro --key-name my-key \
  --user-data ./cloud-init.sh

The CLI should base64-encode the file and include it in the template data.

--volumes

Allow specifying additional EBS volumes beyond the root:

remote ami create-template my-template \
  --ami ami-xxx --instance-type t3.micro --key-name my-key \
  --volume /dev/sdf:20:gp3:encrypted

Format could be device:size_gb:type:encrypted or similar.

Current workaround

Build the launch template JSON manually and use aws ec2 create-launch-template-version directly, which bypasses remote entirely.

Context

Setting up an EC2 Syncthing node required both user-data (for OS hardening + app install) and an extra encrypted EBS volume (for data). Had to drop down to raw AWS CLI for the template creation.