Apply schema mapping to resources

**Motivation**
Following #4703, about introducing a new entity to define and manage a schema mapping by type, the next step is to apply it to resources during creation

**Acceptance criteria**
1. When the schema is not provided by the user, Delta will inject a schema to validate the resource with from this configuration and resource validation will follow the same workflow as if it was provided by the user
2. If no mapping are found for a type, Delta will attempt to make it unconstrained (and return an error if this is not allowed on the enclosing project)

**Not in scope**
1. Updating the schema for resources when the schema mapping configuration is updated.

Start with issue #4703 to understand the schema-mapping entity, then trace resource creation and the existing user-provided schema validation workflow. Apply the mapping only when no schema is supplied, fall back to an unconstrained resource when no mapping exists, and verify the enclosing project's constraints are respected; updating existing resources is out of scope.

Written by the indexing model from the issue text.