[#470] API documentation

Author: jesperpedersen

.github/workflows/ci.yml

@@ -117,6 +117,10 @@ jobs:
       run: brew install cjson
     - name: Install rst2man
       run: brew install docutils
+    - name: Install graphviz
+      run: sudo apt install graphviz
+    - name: Install doxygen
+      run: sudo apt install doxygen
     - name: Install clang
       run: brew install llvm
     - name: Install PostgreSQL