Add optional "interval notation" argument to ValueObjectAttribute for easy range validation

[prlcutting]

Vogen supports custom validation, which is great. But this can be a little repetitive and "boilerplatey" for numeric value objects that require basic range checks, e.g., "value must greater than or equal to zero", or "value cannot exceed 100", etc.

I was wondering if this could be streamlined by the definition of some kind of range validation argument on the ValueObjectAttribute using interval notation:

Interval notation provides a very compact, terse way of expressing min/max values, and whether those values are inclusive/exclusive.

Here are some examples of sample usage (pseudocode):

// Age must be >= 0 and <= 130 years.
[ValueObject<int>(rangeValidation: "[0,130]")]
public partial struct Age { }

// Temperature must be >= absolute zero and has no upper bound.
[ValueObject<double>(rangeValidation: "[-273.15,)")]
public partial struct Celsius { }

// Pipe diameter must be > 0.0 and <= 2.0 meters.
[ValueObject<double>(rangeValidation: "(0,2.0]")]
public partial struct PipeDiameter { }

This would of course source generate the same kind of validation code that I would have otherwise had to define manually, and is the value of this proposal: as a developer I get to define range validation through a terse interval notation, and then all the code to enforce that validation is source generated for me.

Consideration would have to be given as to exactly how this is done, e.g., does it literally write the Validate method for me, and if so, if additional validation was required beyond just range checking, how would that be added, etc. But those are details, and this is clearly far from a design spec, rather, just an initial idea for consideration.

The same concept could perhaps also be used for strings to succinctly express length constraints, e.g.:

// User name must be >= 4 characters long a <= 20 characters long.
[ValueObject<string>(lengthValidation: "[4,20]")]
public partial struct UserName { }

Thoughts?