add ConcreteStructs and simplify SimpleOrbit constructer

[mileslucas]

in response to #23 (comment)

this should be non-breaking, so we can just update the patch version.

[codecov]

Codecov Report

Merging #27 (b679225) into main (262e2d8) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
- Coverage   91.00%   90.99%   -0.02%     
==========================================
  Files          12       12              
  Lines        1012     1010       -2     
==========================================
- Hits          921      919       -2     
  Misses         91       91              

Impacted Files	Coverage Δ
src/Transits.jl	88.88% <ø> (ø)
src/orbits/Orbits.jl	100.00% <ø> (ø)
src/orbits/simple.jl	100.00% <100.00%> (ø)

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[icweaver]

Ohh, ConcreteStructs.jl looks like a super cool package! Looking forward to adding this to KeplerianOrbit. I guess no more {T,L,D,R,A,I,M}, haha

btw, local tests look good on my end. Didn't know about Aqua.jl, it looks really useful too!

[mileslucas]

I'm excited for ConcreteStructs.jl, too. I'm hoping we don't see any issues, cause it saves so much unnecessary type-ing. Yeah, I've been adding Aqua.jl to CI. I've been pretty satisfied with the coverage it adds, although the ambiguities tests fail with anything using ChainRulesCore; I don't know why.