[FEAT] Input validation of mustache templates

[akselthomsen]

Feature Request

Description

Check that a mustache template is technically valid before continuing when reading in a component.

Proposed Solution

Add input validation in ms_initialize().

Also handle type validation in valid_types() and assert_type().

Use Case

When developing a new standard it is useful to get clear error messages when mistakes happen in the mustache template.

Impact

No impact on users, only for standard developers.