VP-1947: Storefront - Auto order frequency resets when you go to the next stage of order creating

[pushnitsa]

Problem

Payment plan don't work correctly

Solution

Period don't change due navigating on order creation

Proposed of changes

Add comparing period case insensitive method.

Additional context (optional)

Make sure these boxes are checked:

• [x] Check all the changes in github PR - files count (non of them are redundant, have meaningful changes, all are added), if target branch is correct
• [x] Check methods and variable namings - it should be self descriptive, no typos
• [x] Check you did not introduce breaking changes in API and public models/services.
• [x] Respect extensibility - https://community.virtocommerce.com/t/extensibility-basics-the-domain-model-and-persistence-layer-extension/141
• [x] Follow DRY and SOLID principles
• [x] For unit tests - follow Microsoft best practices: https://docs.microsoft.com/en-us/dotnet/core/testing/unit-testing-best-practices
• [x] Consolidate solution dependencies in case you are using newer version, update VC module dependencies in module.manifest. Do not upgrade 3rd party packages that are shipped with the platform with the version newer than in the platform.
• [x] Check code style conventions - https://github.com/VirtoCommerce/styleguide/blob/master/csharp.md
• [x] Check PR have a concise and descriptive title, follow git commit message rules

[vc-ci]

SonarQube analysis reported 2 issues

Note: The following issues were found on lines that were not modified in the pull request. Because these issues can't be reported as line comments, they are summarized here:

1. checkout.js#L120: Remove this empty statement.
2. checkout.js#L159: Remove this empty statement.