Configure remote paths

[cbundy]

Adds a new Environment Variable PRIMARY/SECONDARY...PATH for primary and secondary servers

• Allows users to override the default path that their Pi-hole web interface is available under
• Introduces a new class for managing the host configuration
• Handles many combinations of Base URL and Path that could already exist

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This is quite noisy, but I hope I can make up by making sure it's at least well tested....

I tried a simpler approach, but while it worked it left some confusion in the codebase around baseUrl, so I've moved everything to use fullUrl and now we have both path and baseUrl as two separate values. This can be undone if it seems unnecessary.

I've tried to ensure that I catch as many backward compatibility tests it needs, such as if people are already providing some path within their baseUrl (because the need here was to remove the default /admin value only). I've made the assumption that there are people out there who may already be defining some path values in their baseUrl, this approach should not cause any impact for them.

I've never used typescript and I'm not really a practiced JS developer, so let me know if anything seems out of place or where I could make improvements.

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Closes #62

[codecov-commenter]

Codecov Report

Base: 99.55% // Head: 99.58% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (61a84b2) compared to base (00a9dfe).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #68      +/-   ##
==========================================
+ Coverage   99.55%   99.58%   +0.02%     
==========================================
  Files           6        6              
  Lines         225      239      +14     
  Branches       46       51       +5     
==========================================
+ Hits          224      238      +14     
  Misses          1        1              

Impacted Files	Coverage Δ
src/client.ts	100.00% <100.00%> (ø)
src/config.ts	100.00% <100.00%> (ø)
src/notify.ts	98.41% <100.00%> (ø)

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[mattwebbio]

This is awesome! I've just pushed up a prerelease to test. There was one comment that seems to have snuck in to your commits, but I'll run the prerelease for a couple days and once that's addressed this looks good to merge!

[cbundy]

Cheers, I missed running the tests again and forgot before I pushed.