minor mashtree improvements

[kapsakcj]

Setting as draft until I test in Terra. Just noticed that the user cannot alter the docker image used for mashtree and there is no docker output string.

🛠️ Changes Being Made

• expose optional string input docker for mashtree task
• added new String output docker for mashtree task & mashtree_docker String output for the mashtree workflow

🧠 Context and Rationale

More flexibility

📋 Workflow/Task Steps

Inputs

Outputs

🧪 Testing

Locally

Did not test locally, this is a simple change

Terra

Tested successfully in Terra. Was able to pass in an optional docker input string, which was used correctly. Also produced the correct output string/column for mashtree_docker

🔬 Quality checks

Pull Request (PR) checklist:

• Include a description of what is in this pull request in this message.
• The workflow/task has been tested locally and on Terra
• The CI/CD has been adjusted and tests are passing
• Everything follows the style guide

[sage-wright]

Code looks good; running a test here and will approve once completed successfullyl

[sage-wright]

Tests succeeded. Now merging to main!