Adjust AWS keys for Archivematica SIPs

Why these changes are being introduced:

We recently merged a proposed solution to this. However, looking
back at ETD-600, I realized I have the spec wrong. The current keys
are missing the graduation year and month.

Relevant ticket(s):

https://mitlibraries.atlassian.net/browse/ETD-593

How this addresses that need:

This updates the keys to what Joe originally requested, so that
the SIP directory includes the grad month and is nested beneath
the grad year. For example: `etdsip/2023/June-2023_001`

Side effects of this change:

None.

app/models/submission_information_package_zipper.rb

@@ -19,7 +19,8 @@ def initialize(sip)
   # This key needs to be unique. By default, ActiveStorage generates a UUID, but since we want a file path for our
   # Archivematica needs, we are generating a key. We handle uniqueness on the `bag_name` side.
   def keygen(sip)
-    "etdsip/#{sip.thesis.accession_number}/#{sip.bag_name}.zip"
+    thesis = sip.thesis
+    "etdsip/#{thesis.graduation_year}/#{thesis.graduation_month}-#{thesis.accession_number}/#{sip.bag_name}.zip"
   end
 
   # bagamatic takes a sip, creates a temporary zip file, and returns that file

test/models/submission_information_package_zipper_test.rb

@@ -45,6 +45,6 @@ def setup_thesis
     SubmissionInformationPackageZipper.new(sip)
 
     blob = thesis.submission_information_packages.last.bag.blob
-    assert blob.key.starts_with? "etdsip/#{thesis.accession_number}"
+    assert blob.key.starts_with? "etdsip/#{thesis.graduation_year}/#{thesis.graduation_month}-#{thesis.accession_number}"
   end
 end