Scopes should have some validation

[spilliams]

as a safety feature. I would like terrascope to stop me if I've mistyped my scope values, or if I use a duplicate scope value, or if I put weird characters in my scope value that would not play nicely with the places that value ends up (e.g. state bucket path).

I would also like terrascope to stop me if I've misconstrued the scope patterns (for example, put a "Red" domain artifact in the "Gold" platform instead of the "Silver" platform)

The AC for this ticket is that:

1. there is a schema for setting validation on a scope type
2. when running a project, it will raise an error if any of the scope data does not conform to the validation

Other tickets will cover other topics about this feature.

[spilliams]

When parsing a block, you can set a context. If you give the context Values and Functions then you can use those during the decoding. Something like:

ctx := &hcl.EvalContext{
    Variables: map[string]cty.Value{
        "scope": cty.ObjectVal(map[string]cty.Value{
            "value":
        })
    },
    // shamelessly stolen from Terraform
    // https://github.com/hashicorp/terraform/blob/f8669d235174ebdaf503d1cd400e22eb51c74c3b/internal/lang/functions.go
    Functions: map[string]function.Function{
        "abs":             stdlib.AbsoluteFunc,
        "can":             tryfunc.CanFunc,
        "ceil":            stdlib.CeilFunc,
        "chomp":           stdlib.ChompFunc,
        "coalescelist":    stdlib.CoalesceListFunc,
        "compact":         stdlib.CompactFunc,
        "concat":          stdlib.ConcatFunc,
        "contains":        stdlib.ContainsFunc,
        "csvdecode":       stdlib.CSVDecodeFunc,
        "distinct":        stdlib.DistinctFunc,
        "element":         stdlib.ElementFunc,
        "chunklist":       stdlib.ChunklistFunc,
        "flatten":         stdlib.FlattenFunc,
        "floor":           stdlib.FloorFunc,
        "format":          stdlib.FormatFunc,
        "formatdate":      stdlib.FormatDateFunc,
        "formatlist":      stdlib.FormatListFunc,
        "indent":          stdlib.IndentFunc,
        "join":            stdlib.JoinFunc,
        "jsondecode":      stdlib.JSONDecodeFunc,
        "jsonencode":      stdlib.JSONEncodeFunc,
        "keys":            stdlib.KeysFunc,
        "log":             stdlib.LogFunc,
        "lower":           stdlib.LowerFunc,
        "max":             stdlib.MaxFunc,
        "merge":           stdlib.MergeFunc,
        "min":             stdlib.MinFunc,
        "parseint":        stdlib.ParseIntFunc,
        "pow":             stdlib.PowFunc,
        "range":           stdlib.RangeFunc,
        "regex":           stdlib.RegexFunc,
        "regexall":        stdlib.RegexAllFunc,
        "reverse":         stdlib.ReverseListFunc,
        "setintersection": stdlib.SetIntersectionFunc,
        "setproduct":      stdlib.SetProductFunc,
        "setsubtract":     stdlib.SetSubtractFunc,
        "setunion":        stdlib.SetUnionFunc,
        "signum":          stdlib.SignumFunc,
        "slice":           stdlib.SliceFunc,
        "sort":            stdlib.SortFunc,
        "split":           stdlib.SplitFunc,
        "strrev":          stdlib.ReverseFunc,
        "substr":          stdlib.SubstrFunc,
        "timeadd":         stdlib.TimeAddFunc,
        "title":           stdlib.TitleFunc,
        "trim":            stdlib.TrimFunc,
        "trimprefix":      stdlib.TrimPrefixFunc,
        "trimspace":       stdlib.TrimSpaceFunc,
        "trimsuffix":      stdlib.TrimSuffixFunc,
        "try":             tryfunc.TryFunc,
        "upper":           stdlib.UpperFunc,
        "values":          stdlib.ValuesFunc,
        "zipmap":          stdlib.ZipmapFunc,
    },
}