Update Cache Config To Use TimeSpan

[JimBobSquarePants]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following matches the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
• I have provided test coverage for my change (where applicable)

Description

Updates configuration to allow caching by any TimeSpan configuration. See #104

This is a necessary breaking change.

I've also reintroduced the samples webapp into the solution.

[codecov]

Codecov Report

Merging #111 into master will decrease coverage by 0.22%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master     #111      +/-   ##
==========================================
- Coverage   82.89%   82.67%   -0.23%     
==========================================
  Files          44       44              
  Lines        1076     1068       -8     
  Branches      158      157       -1     
==========================================
- Hits          892      883       -9     
- Misses        136      137       +1     
  Partials       48       48              

Flag	Coverage Δ
#unittests	82.67% <83.33%> (-0.23%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...Web/DependencyInjection/ImageSharpConfiguration.cs	100.00% <ø> (ø)
src/ImageSharp.Web/Middleware/ImageContext.cs	71.08% <50.00%> (-1.33%)	⬇️
.../ImageSharp.Web/Middleware/ImageSharpMiddleware.cs	78.00% <100.00%> (ø)
...harp.Web/Middleware/ImageSharpMiddlewareOptions.cs	53.84% <100.00%> (-3.85%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update eec9fe8...054bc81. Read the comment docs.

[tocsoft]

I do think I would just make more sense to just have a single option called MaxCacheTimeout and it be of type TimeSpan instead of the now 3 separate parts it then allows for super fine grained adjustments without have to keep adding additional properties and having to then coherence the multiple fields into a TimeSpan anyway.

[JimBobSquarePants]

Yeah, we'd have to determine a format though that can be parsed invariantly.

[tocsoft]

TimeSpans just work for serializing/parsing, if we are loading from app.configs anyway.

[tocsoft]

https://docs.microsoft.com/en-us/dotnet/standard/base-types/standard-timespan-format-strings

The invariant format looks like this 3.17:25:30.5000000 [d'.']hh':'mm':'ss['.'fffffff] so generally HH:MM:SS with optional days prefix and milliseconds postfix

[JimBobSquarePants]

TimeSpans just work for serializing/parsing, if we are loading from app.configs anyway.

Beautiful. I'll make the changes.

[JimBobSquarePants]

We'll have to do this in all our repos. They've changed things which causes a 400

[tocsoft]

much better 👍