CloudMigrations: Implement snapshot management apis (#89296)

* add new apis

* add payloads

* create snapshot status type

* add some impl

* finish implementing update

* start implementing build snapshot func

* add more fake build logic

* add cancel endpoint. do some cleanup

* implement GetSnapshot

* implement upload snapshot

* merge onprem status with gms result

* get it working

* update comment

* rename list endpoint

* add query limit and offset

* add helper method to snapshot

* little bit of cleanup

* work on swagger annotations

* manual merge

* generate swagger specs

* clean up curl commands

* fix bugs found during final testing

* fix linter issue

* fix unit test

pkg/services/cloudmigration/api/curl_commands.txt

@@ -0,0 +1,21 @@
+[sample token] // NOT A REAL TOKEN
+eyJUb2tlbiI6ImNvbXBsZXRlbHlfZmFrZV90b2tlbl9jZG9peTFhYzdwdXlwZCIsIkluc3RhbmNlIjp7IlN0YWNrSUQiOjEyMzQ1LCJTbHVnIjoic3R1Ymluc3RhbmNlIiwiUmVnaW9uU2x1ZyI6ImZha2UtcmVnaW9uIiwiQ2x1c3RlclNsdWciOiJmYWtlLWNsdXNlciJ9fQ==
+
+[create session}
+curl -X POST -H "Content-Type: application/json" \
+  http://admin:admin@localhost:3000/api/cloudmigration/migration \
+  -d '{"AuthToken":"eyJUb2tlbiI6ImNvbXBsZXRlbHlfZmFrZV90b2tlbl9jZG9peTFhYzdwdXlwZCIsIkluc3RhbmNlIjp7IlN0YWNrSUQiOjEyMzQ1LCJTbHVnIjoic3R1Ymluc3RhbmNlIiwiUmVnaW9uU2x1ZyI6ImZha2UtcmVnaW9uIiwiQ2x1c3RlclNsdWciOiJmYWtlLWNsdXNlciJ9fQ=="}'
+
+[create snapshot]
+curl -X POST -H "Content-Type: application/json" \
+  http://admin:admin@localhost:3000/api/cloudmigration/migration/{sessionUid}/snapshot
+
+[get snapshot list]
+curl -X GET http://admin:admin@localhost:3000/api/cloudmigration/migration/{sessionUid}/snapshots?limit=100&offset=0
+
+[get snapshot]
+curl -X GET http://admin:admin@localhost:3000/api/cloudmigration/migration/{sessionUid}/snapshot/{snapshotUid}
+
+[upload snapshot]
+curl -X POST -H "Content-Type: application/json" \
+   http://admin:admin@localhost:3000/api/cloudmigration/migration/{sessionUid}/snapshot/{snapshotUid}/upload