v14: Return all data types from DataTypeService.GetAllAsync()

[ronaldbarendse]

PR #14665 added GetAllAsync(params Guid[] keys) to IDataTypeService, but the implementation returns 0 data types when no keys are specified, which is different to the existing GetAll(params int[] ids) that returns all data types of no IDs are specified.

This PR fixes the GetAllAsync() implementation and also removes some unnecessary async/awaits (on methods that use Task.FromResult().

[kjac]

This is a dangerous change of behaviour, but I get the reasoning behind. Fortunately our tests uncovered the breakage 😄 I have amended the PR to ensure that we don't accidentally load all data types when we mean to load none.

[kjac]

💪 👍

[ronaldbarendse]

This is a dangerous change of behaviour, but I get the reasoning behind. Fortunately our tests uncovered the breakage 😄 I have amended the PR to ensure that we don't accidentally load all data types when we mean to load none.

Hmm, very true indeed! We could fix this by adding an overload without the parameter, so GetAllAync() returns all, but GetAllAsync(Array.Empty<Guid>()) returns nothing, as it explicitly uses the key parameter (that would allow for removing your amends again)...

To avoid any confusion, a better solution would probably be to have separate method names, e.g. GetAllAsync() and GetAllByKeysAsync(params Guid[] keys) (or even just GetAsync(params Guid[] keys), although that would change the return type based on how many/which parameters you specify).