Replace date replace var with an empty string on terms.

[hansjovis]

Context

• Since terms do not have a published date, we do not want to output anything when a user enters a %%date%% replace var in the title or meta description of a term.

Summary

This PR can be summarized in the following changelog entry:

• Fixes a bug where the date replacement variable would output 0 when used in categories or tags, instead of not outputting anything as shown in the Google preview.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

Please test this in a 'normal' term (either category or tag) and in a term from a custom taxonomy.

• Create a term.
• Add the %%date%% replace var in either the meta description or SEO title.
• See that the Google preview replaces the replace var with nothing.
• Publish the term.
• Go to the term page on the website.
• Check the source code of the term page. It should be the same as the one shown in the Google preview.
  • E.g. the %%date%% replace var should be replaced by nothing / the empty string.
  • Note: There is another existing bug where empty strings are replaced with a single space.

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Other environments

• This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• I have written documentation for this change.

Quality assurance

• I have tested this code to the best of my abilities
• I have added unittests to verify the code works as intended
• If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• I have written this PR in accordance with my team's definition of done.

Fixes #

[IreneStr]

@hansjovis Is this still relevant, or can it be closed? :)