aws sts get-call-identity doesn't work for correct AWS_EC2_METADATA_SERVICE_ENDPOINT

[darren-wen]

Describe the bug

export AWS_EC2_METADATA_SERVICE_ENDPOINT=http://localhost.trade-dev.flexport.com:59279
aws sts get-caller-identity

Invalid endpoint EC2 Instance Metadata endpoint: http://localhost.trade-dev.flexport.com:59279latest/api/token

if I add a / at the end, the aws cli works, but the java SDK breaks.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

the aws cli can work with http://localhost.trade-dev.flexport.com:59279(no trailing /)

Current Behavior

the aws cli doesn't work with http://localhost.trade-dev.flexport.com:59279, it throws

Invalid endpoint EC2 Instance Metadata endpoint: http://localhost.trade-dev.flexport.com:59279latest/api/token

Reproduction Steps

export AWS_EC2_METADATA_SERVICE_ENDPOINT=http://localhost.trade-dev.flexport.com:59279 # make sure you have a valid endpoint like this
aws sts get-caller-identity

Possible Solution

It looks like the aws cli implementation literally appends the latest/api/token to the endpoint to construct the final URL. We can use some URL tools to construct the final URL to avoid the / issue.

Additional Information/Context

No response

CLI version used

aws-cli/2.23.13 Python/3.12.8 Darwin/23.6.0 source/arm64

Environment details (OS name and version, etc.)

macOS Sonoma Version 14.7 (23H124)

[ashovlin]

Likely addressed via #8967