[MM-31790] Support Packet Generation BACKEND (#16667)

* init commit

* clean up the code

* make mocks

* fix translations

* mocks and lint fixes

* add tests

* little fixes

* Update i18n/en.json

Co-authored-by: Scott Bishel <scott.bishel@mattermost.com>

* Update i18n/en.json

Co-authored-by: Scott Bishel <scott.bishel@mattermost.com>

* Update i18n/en.json

Co-authored-by: Scott Bishel <scott.bishel@mattermost.com>

* Update i18n/en.json

Co-authored-by: Scott Bishel <scott.bishel@mattermost.com>

* Update i18n/en.json

Co-authored-by: Scott Bishel <scott.bishel@mattermost.com>

* Address Comments

* fix i18n

* update api endpoint

* add enable file and file level for conditional show of banner

* Address Comments

* Make it more clear about returns

* Create zip file utility function

* update en.json

* address comments

* write tests

* check for data in test

* remove warning string

* Correct expected and actual

* set database through environment variables

* reset environment variable at end of test

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
Co-authored-by: Scott Bishel <scott.bishel@mattermost.com>

i18n/en.json

@@ -1580,6 +1580,10 @@
     "id": "api.migrate_to_saml.error",
     "translation": "Unable to migrate SAML."
   },
+  {
+    "id": "api.no_license",
+    "translation": "E10 or E20 license required to use this endpoint."
+  },
   {
     "id": "api.oauth.allow_oauth.redirect_callback.app_error",
     "translation": "invalid_request: Supplied redirect_uri did not match registered callback_url."
@@ -3050,6 +3054,18 @@
     "id": "api.templates.welcome_subject",
     "translation": "[{{ .SiteName }}] You joined {{ .ServerURL }}"
   },
+  {
+    "id": "api.unable_to_create_zip_file",
+    "translation": "Error creating zip file."
+  },
+  {
+    "id": "api.unable_to_read_file_from_backend",
+    "translation": "Error reading file from backend"
+  },
+  {
+    "id": "api.unable_write_file_response",
+    "translation": "Error downloading support packet file."
+  },
   {
     "id": "api.upgrade_to_enterprise.already-done.app_error",
     "translation": "You have already upgraded to Mattermost Enterprise Edition. Please restart the server to finish the upgrade."