Metadata database model

Instead of creating 100 columns in a table for data that might or might not exist, we use another table called xMetadata (replacing x with a model name).

Columns

Name	Type	Default value	Constraints & Validations
id	Integer (unsigned)		PRIMARY KEY AUTO_INCREMENT
key	String		NOT NULL
value	LongText	null	NULL
valueType	String	'NULL'	NOT NULL
foreign_key	String | Integer (unsigned)		NOT NULL (linked to id of non-metadata model/table)

All data can be stored under keys. The type of keys that are used depends on the model.