Fix JSON::Deserialize not working with column_name field

[dukeraphaelng]

Description

• Full detail of issue here: https://github.com/anykeyh/clear/issues/202
• This issue is a simple error due to the use of COLUMNS key for declaring instance variables, which is assigned as follows:

https://github.com/anykeyh/clear/blob/3bdaa44a7d0382fd8f6846afe8b8da95d58d9452/src/clear/model/modules/has_columns.cr#L174

The key is assigned to the method name, name.var by default but will be re-assigned to column_name.id if declared, which is the name of the column in the database, not the name of the method.

We need to use the method name and not the column_name, hence the change from {{name.id}} to {{settings["crystal_variable_name"]}}

Motivation and Context

• Resolves https://github.com/anykeyh/clear/issues/202

How Has This Been Tested?

• All specs passed

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

• [ ] Manual of usage of the new feature.

Checklist:

• [x] My code follows the code style of this project. bin/ameba ran without alert.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.