feat: some field type should have a default value

[magrinj]

Scope & Context

Field type like TEXT should have a default value of empty string instead of null.

Current behavior

If we don't have a default value provided, this one is set to null.

Expected behavior

Some field type should have a default value instead of null.
By example TEXT should have the default value "".

Technical inputs

This is only applying to the FieldMetadata.