Content entry frontmatter does not match schema.

Example error message:
blog → post.md frontmatter does not match collection schema.
“title” is required.
“date” must be a valid date.

What went wrong?

A Markdown or MDX entry in src/content/ does not match its collection schema. Make sure that all required fields are present, and that all fields are of the correct type. You can check against the collection schema in your src/content/config.* file. See the Content collections documentation for more information.