rework cmake configs

[luca-schlecker]

This PR partly fixes #160

It restructures the CMake system quite a bit.

It is adding:

• FetchContent support
• A proper CMake target
• FindPackage support
• Almost all examples on machines compiling with MSVC (+2 fixes)
• Submodule support
• Unittest now compiles without compression support. (Instead gives a status message)
• Optional installation step

It is removing:

• The need for #define CROW_ENABLE_SSL and #define CROW_ENABLE_COMPRESSION (Except if the amalgam is used)

Left to do:

• Get the documentation up to date

[The-EDev]

Now that the checks are passing I think this PR might be ready to merge. On a side note, I mean no offense with the next part, but you probably know this PR clashes with #147, so what I was wondering is if there's anything that PR has or does that this one doesn't. I'm asking because I'm not that experienced with CMake.

[luca-schlecker]

This PR wasn't even supposed to be done at the moment.
But I see what you mean. Then I'll leave that part out because he already did it.
I'll change this PR out of draft state as soon as I get a last look at it and am happy with it. 👍

[The-EDev]

But I see what you mean. Then I'll leave that part out because he already did it.

That wasn't what I meant, You seemed to take a different approach to get FindPackage working, and I was wondering which way was better.. Sorry for the misunderstanding

[luca-schlecker]

I have no FindPackage code in this PR. Mine would have looked almost like his, from what I've seen.

[The-EDev]

Hmmm, I understand, thanks for clarifying

[The-EDev]

CMake Error at /usr/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:146 (message):
Could NOT find OpenSSL, try to set the path to OpenSSL root folder in the
system variable OPENSSL_ROOT_DIR (missing: OPENSSL_CRYPTO_LIBRARY
OPENSSL_INCLUDE_DIR)

[The-EDev]

Coverage here is incorrect, it's being pulled from when some tests were disabled (I believe), the newer tests give a 500 error, I was informed by Coveralls that this is due to some downtime they've been having and should be fixed in time.

[The-EDev]

okay for some reason coverage went down to 66%...

[luca-schlecker]

I have a hunch where it might be coming from.

diff --git a/.travis.yml b/.travis.yml
index eb59f5b7c8..7c49755b7b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -33,6 +33,7 @@ addons:
       - mkdocs
       - graphviz
       - zlib1g-dev
+      - libssl-dev
 
 before_install:
   - if [ "$TRAVIS_COMPILER" == "gcc" -a "$TRAVIS_CPU_ARCH" == "amd64" ]; then export PUSH_COVERAGE=ON; fi
@@ -45,7 +46,7 @@ before_script:
   - mkdir build
   - cd build
   - cmake --version
-  - cmake ..
+  - cmake .. -DCROW_ENABLE_COMPRESSION=ON -DCROW_ENABLE_SSL=ON

I've enabled SSL in the CI build, leading to CROW_ENABLE_SSL being defined, and thus SSL code is enabled. Maybe Coverall didn't care before because the code was disabled by:

#ifdef CROW_ENABLE_SSL
...
#endif

Now though, it is enabled but no tests exist for the now accessible code.

[The-EDev]

hmmm, we could undefine CROW_ENABLE_SSL at the unittest, or get #130 working. what do you suggest?

[luca-schlecker]

I think getting some SSL tests up and running is the proper way to up the coverage again.

[The-EDev]

I'll merge this into a separate branch, Add documentation and SSL tests, and merge everything into master. Thanks again for all your help.