Resolve "EXTERN: Adapt to Conan 2"

Summary

Updating from Conan 1 to Conan 2.5 required several changes, both on the conanfile.py as well as the CMakeLists.txt file(s).

Related to

• #73 (closed)
• #80 (closed)
• #82 (closed)
• #83 (closed)

Related MR for integration tests: caosdb-cppinttest!35 (merged)

Focus

The biggest changes are in conanfile.py and CMakeLists.txt all according to the migration guide. Crucial here are

• Conan now doesn't appear in the CMakeLists.txt files anymore. Instead, Conan generates CMakeToolChain files, which handle all the necessary includes etc. The toolchain files are passed to CMake as arguments.
• Packages are included in our CMakeLists.txt using CMake's FindPackage
• Conan 2.0 builds into build/<build_type>, i.e. build/Release or build/Debug

Test Environment

How to set up a test environment for manual testing?

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• All automated tests pass
• Reference related issues
• Up-to-date CHANGELOG.md (or not necessary)
• Up-to-date JSON schema (or not necessary)
• Appropriate user and developer documentation (or not necessary)
  • How do I use the software? Assume "stupid" users.
  • How do I develop or debug the software? Assume novice developers.
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
• Appropriate user and developer documentation (or not necessary)
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

For further good practices have a look at our review guidelines.

doc/Install_develop.rst

@@ -180,15 +180,15 @@ Build
 For the tests the build type has to be Debug. As a shorthand you can run ``make
 test``. If you want to build manually, follow these steps:
 
-1. ``conan install . -s build_type=Debug``
-2. ``cd build/Debug``
-3. ``cmake -B . -D CMAKE_BUILD_TYPE=Debug ..``
+1. ``conan install . -s build_type=Debug --build=missing``
+2. ``cd build/Debug`` 
+3. ``cmake -S ../.. -G "Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=generators/conan_toolchain.cmake  -DCMAKE_POLICY_DEFAULT_CMP0091=NEW -DCMAKE_BUILD_TYPE=Debug``
     - If your clang-format version is too old, formatting, linting etc. can
       be skipped:
       ``cmake -B . -D CMAKE_BUILD_TYPE=Debug -D SKIP_LINTING=ON ..``
     - Depending on the clang version it may be necessary to also add
       ``-DCMAKE_CXX_FLAGS="-Wno-unused-parameter"``
-4. ``cmake --build .``
+5. ``cmake --build . ``
     - If this fails with ``Error running '': No such file or directory``, you may want to try
       CMake's ``-D SKIP_LINTING=ON``. (See previous step.)