Allow whitespace in foreignKey array / array type attribute definition

## Issue

Currently the codegenerator fails when an array-type attribute, i.e. a foreignKey array or a plain array is defined with whitespaces in the definition.

For example: `"[String ]"` or `"[ String]"`. Only the definition `"[String]"` does not fail.

Align the behaviour of the spa-codegen to the graphql-server-model-codgen where whitespaces are allowed.