Add member_id to the member_months_key grain

[davidshimamoto]

Describe your changes

Updated member_months to include member_id in the creation of the member_months_key

How has this been tested?

dbt run -s claims_enrollment__member_months
Verified the change in key values

Reviewer focus

Please summarize the specific items you’d like the reviewer(s) to look into.

Checklist before requesting a review

• I have added at least one Github label to this PR (bug, enhancement, breaking change,...)
• My code follows style guidelines
• (New models) YAML files are categorized by sub folder and models listed in alphabetical order
• (New models) I have added a config to each new model to enable it for claims and/or clinical data
• (New models) I have added the variable tuva_last_run to the final output
• (Optional) I have recorded a Loom to explain this PR

Package release checklist

• I have updated dbt docs
• I have updated the version number in the dbt_project.yml

(Optional) Gif of how this PR makes you feel

Loom link

[davidshimamoto]

After further consideration, abandoning this. We will instead keep the current grain and adjust logic as the current grain is what we want.