feat: support virtual fields (fixes #204)

[vobu]

No description provided.

[vobu]

converted to draft until cds^5.5 is available

[David-Kunz]

Hi @vobu ,

You can implement virtual field handling by substituting them:

{ 
  SELECT: {
    ...,
    columns: [
      { ref: ['myVirtualField'] }
    ]
}

to

{ 
  SELECT: {
    ...,
    columns: [
      { val: null, as: ['myVirtualField'] }
    ]
}

Notes:

• Virtual fields can also appear in structured elements or expands
• If they have a default value, you can replace null with it

Best regards,
David

[vobu]

You can implement virtual field handling by substituting them:

thx for the hint, we just plugged into the core logic and got this going :)

[vobu]

@gregorwolf please re-review