Sample web API server on Rust

There are r2d2 and bb8 based implementations here, as well as asp.net for comparison.

This does

1. Adds a note to PostgreSQL.
2. Returns a note from PostgreSQL.
3. Returns current date.

Results

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19042
Intel Core i7-8750H CPU 2.20GHz (Coffee Lake), 1 CPU, 12 logical and 6 physical cores
.NET Core SDK=5.0.101
  [Host]     : .NET Core 5.0.1 (CoreCLR 5.0.120.57516, CoreFX 5.0.120.57516), X64 RyuJIT
  DefaultJob : .NET Core 5.0.1 (CoreCLR 5.0.120.57516, CoreFX 5.0.120.57516), X64 RyuJIT

ASP.NET

Method	Parallel	Path	Mean	Error	StdDev	Median
Benchmark	True	GET /date	9.764 ms	0.1692 ms	0.1500 ms	9.713 ms
Benchmark	False	GET /date	43.043 ms	0.8405 ms	0.7862 ms	42.742 ms
Benchmark	True	POST & GET	589.727 ms	40.3020 ms	118.8312 ms	596.048 ms
Benchmark	False	POST & GET	3,157.214 ms	231.7176 ms	675.9310 ms	3,165.454 ms

BB8

Method	Parallel	Path	Mean	Error	StdDev	Median
Benchmark	True	GET /date	9.054 ms	0.2258 ms	0.6478 ms	8.990 ms
Benchmark	False	GET /date	37.105 ms	0.7373 ms	1.6941 ms	36.482 ms
Benchmark	True	POST & GET	888.076 ms	48.6239 ms	142.605 ms	867.573 ms
Benchmark	False	POST & GET	5,031.185 ms	368.6956 ms	1,087.107 ms	4,895.177 ms

R2D2

Method	Parallel	Path	Mean	Error	StdDev	Median
Benchmark	True	GET /date	8.945 ms	0.2274 ms	0.6596 ms	8.935 ms
Benchmark	False	GET /date	39.317 ms	0.7753 ms	1.7969 ms	38.967 ms
Benchmark	True	POST & GET	976.429 ms	51.5924 ms	152.1214 ms	966.551 ms
Benchmark	False	POST & GET	5,042.993 ms	281.0737 ms	828.7520 ms	5,045.977 ms