test(e2e): Add database migration test (#2627)

* test(e2e): Add database migration test

* chore(enos): Add enos scenario for migration test

* chore(enos): Update go test command to use count option

* doc(e2e): Update readme with migration test details

* Fix: Typo

* CR: Use different library

* CR: Add additional context in comment

* CR: Move some code from test into functions

* doc(e2e): Add instructions to more easily retrieve environment variables

* refact(e2e): Create some more methods to increase test readability

testing/internal/e2e/tests/database/testdata/credential.json

@@ -0,0 +1,4 @@
+{
+    "a": "test",
+    "b": "foo"
+}