Default value for attributes

**Is your feature request related to a problem? Please describe.**
When creating a new Node or Edge, fields are empty.

**Describe the solution you'd like**
It would be nice to have default values in it.

Therefore it is needed to be able to define it when creating a new attribute or when modifying a column

**Describe alternatives you've considered**
None

**Additional context**
None

Start by tracing the Node and Edge creation flow, then inspect the UI for creating attributes and modifying columns. Define how a default is entered and stored, and verify that newly created Node and Edge fields receive it while existing data remains unaffected.

Written by the indexing model from the issue text.