Fixes visibility param in ProjectSnippet REST API

This renames a param requirement in the ProjectSnippet
REST API update endpoint which was incorrectly
set to visibility_level

changelogs/unreleased/vij-fix-project-snippet-param.yml

+---
+title: Fix visibility param for ProjectSnippet REST endpoint
+merge_request: 40966
+author:
+type: fixed

lib/api/project_snippets.rb

@@ -95,7 +95,7 @@ module API
         optional :visibility, type: String,
                               values: Gitlab::VisibilityLevel.string_values,
                               desc: 'The visibility of the snippet'
-        at_least_one_of :title, :file_name, :content, :visibility_level
+        at_least_one_of :title, :file_name, :content, :visibility
       end
       # rubocop: disable CodeReuse/ActiveRecord
       put ":id/snippets/:snippet_id" do

spec/requests/api/project_snippets_spec.rb

@@ -329,6 +329,13 @@ RSpec.describe API::ProjectSnippets do
       expect(snippet.description).to eq(new_description)
     end
 
+    it 'updates snippet with visibility parameter' do
+      expect { update_snippet(params: { visibility: 'private' }) }
+        .to change { snippet.reload.visibility }
+
+      expect(snippet.visibility).to eq('private')
+    end
+
     it 'returns 404 for invalid snippet id' do
       update_snippet(snippet_id: non_existing_record_id, params: { title: 'foo' })
 
@@ -340,6 +347,7 @@ RSpec.describe API::ProjectSnippets do
       update_snippet
 
       expect(response).to have_gitlab_http_status(:bad_request)
+      expect(json_response['error']).to eq 'title, file_name, content, visibility are missing, at least one parameter must be provided'
     end
 
     it 'returns 400 if content is blank' do