Verify URL before making the request, fixes #527, fixes #545.

[fredrikekre]

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[codecov-commenter]

Codecov Report

Merging #703 (3bb323c) into master (7eca199) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #703      +/-   ##
==========================================
+ Coverage   75.20%   75.26%   +0.06%     
==========================================
  Files          36       36              
  Lines        2363     2369       +6     
==========================================
+ Hits         1777     1783       +6     
  Misses        586      586              

Impacted Files	Coverage Δ
src/RedirectRequest.jl	77.41% <100.00%> (+5.41%)	⬆️

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[fredrikekre]

I just noticed https://github.com/JuliaWeb/URIs.jl/blob/62a77a5b97ac1a5709c17baa1928b77d792d93b1/src/URIs.jl#L288 so perhaps that should be used? It checks a lot more than the bare minimum as this PR does, but perhaps that is fine.

Edit: Doesn't complain about missing host, but I added this as an extra check too.
Edit 2: Removed it, threw in tests for

julia> uri = URI("ws://127.0.0.1:8086/query?k1=v1&k2=v2")
URI("ws://127.0.0.1:8086/query?k1=v1&k2=v2")

julia> isvalid(uri)
false

but maybe that is just a bad test case...