Emit warning of aws/assume-role deprecation

aws/assume-role/mint-leaf.yml

@@ -1,5 +1,5 @@
 name: aws/assume-role
-version: 1.1.3
+version: 1.1.4
 description: Assume an AWS role
 source_code_url: https://github.com/rwx-research/mint-leaves/tree/main/aws/assume-role
 issue_tracker_url: https://github.com/rwx-research/mint-leaves/issues
@@ -32,6 +32,11 @@ tasks:
     run: |
       set -ueo pipefail
 
+      cat << EOF > $(mktemp "$MINT_WARNINGS/warning-XXXX")
+      This leaf is deprecated. Please upgrade to \`2.0.0\` or later.
+      Going forward the OIDC token is provided by downstream tasks via AWS_OIDC_TOKEN environment variable.
+      EOF
+
       if ! command -v aws &> /dev/null; then
         cat << EOF > $(mktemp "$MINT_ERRORS/error-XXXX")
       The AWS CLI must be installed. To install it, you can use the \`aws/install-cli\` leaf.