Strip whitespace from saml group link name

What does this MR do?

This MR adds a method to strip any preceeding and succeeding whitespace from the saml_group_name parameter before it's saved on the saml_group_link.rb model.

Without this, whitespace that's entered by accident when creating a SAML Group Link will be included in the name, and due to #339797 (closed) the user will not be able to notice the whitespace on the GUI after it's saved, potentially causing groups not to match and difficult troubleshooting.

Closes #339797 (closed)

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Does this MR meet the acceptance criteria?

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