Add `name` keyword to macros

[odow]

Motivated by https://discourse.julialang.org/t/getting-started-mip-variables-and-datastructure/63766/6

It would be nice to have

model = Model()
@variable(model, x[i=1:3], name="x_$(i)")

Currently there is

model = Model()
julia> @variable(model, x[i=1:3], base_name="x_$(i)")
3-element Vector{VariableRef}:
 x_1[1]
 x_2[2]
 x_3[3]

which isn't quite the same thing.

[jd-foster]

At the risk of over-complicating things since the issue is originally about variable naming, if this approach was used consistently in @constraint too, then it might be used to address the ambiguity in "naming when broadcasting" as discussed in #1166. It also seems possible to address #1936 if a function (returning a string) can know about the constraint (base) name and the index. (Really getting into the weeds, potentially addresses #2171 too....)

[odow]

At the risk of over-complicating things since the issue is originally about variable naming

It's worth thinking about this holistically prior to JuMP 1.0 in order to make sure we get it right. The number of open issues around naming suggests that the design could do with improvements.

[odow]

Having thought about this more, I don't think we need this. It's added complexity, and will lead to confusion between name and base_name. It's not hard to loop over variables and set their name to something else if you don't like JuMP's default names.

[jd-foster]

Is it worth adding your nice answer in https://discourse.julialang.org/t/how-to-register-the-name-of-anonymous-variable-to-certain-model/69273/2 to the documentation somewhere?

[odow]

Does this cover it? https://jump.dev/JuMP.jl/dev/manual/variables/#Variable-names

[jd-foster]

Looks like it's all covered there. I thought the dot points might serve as a good recap all together at the end of the section e.g. "In summary, ..." but may be too repetitive.

[odow]

Open a PR if you have suggestions for improvements. The recap might be good at the end of the first section?

[jd-foster]

OK, will have a read through again and see if it would help.