Provide helpful error when dashes are used in path variables

[matthewmcgarvey]

Purpose

The error message given when using a dash in a path variable is unhelpful to solving the issue. Changing the message allows users to fix the issue.

Fixes #1235

Description

Before

There was a problem expanding macro 'add_route'

Code in macro 'match'

 5 | add_route(:get, "/test/:param-1/:param_2", TestParamAction)
     ^
Called macro defined in src/lucky/routable.cr:191:3

 191 | macro add_route(method, path, action)

Which expanded to:

 >  7 |     
 >  8 |       
 >  9 |       def param-1 : String
                      ^
Error: unexpected token: -1

After

Showing last frame. Use --error-trace for full trace.

There was a problem expanding macro 'get'

Code in spec/lucky/action_route_params_spec.cr:6:3

 6 | get "/test/:param-1/:param_2" do
     ^
Called macro defined in macro 'macro_4475664912'

 19 | macro get(path)

Which expanded to:

 > 1 | match(:get, "/test/:param-1/:param_2") do
       ^
Error: Path variables must only use underscores. Use ":param_1" instead of ":param-1".

Checklist

• - An issue already exists detailing the issue/or feature request that this PR fixes
• - All specs are formatted with crystal tool format spec src
• - Inline documentation has been added and/or updated
• - Lucky builds on docker with ./script/setup
• - All builds and specs pass on docker with ./script/test

[jwoertink]

👍

[paulcsmith]

Looks great. Thanks @matthewmcgarvey!