ci: use conda to render docs

[ci docs]

.gitlab/ci/docs.yml

@@ -4,13 +4,27 @@
 # Build and deploy the Doxygen documentation.
 # ----------------------------------------------------------------------
 
+include:
+  # https://computing.docs.ligo.org/gitlab-ci-templates/
+  - project: computing/gitlab-ci-templates
+    # https://computing.docs.ligo.org/gitlab-ci-templates/conda/
+    file: conda.yml
+
 documentation:
-  image: igwn/lalsuite-dev:bullseye
+  image: igwn/base:conda
+  # https://computing.docs.ligo.org/gitlab-ci-templates/conda/#.conda:base
+  extends: .conda:base
   stage: documentation
   needs: []
+  before_script:
+    - !reference [".conda:base", "before_script"]
+    # install conda environment
+    - mamba env create -n lalsuite-docs -q -f common/conda/environment.yml
+    - mamba install -y -q -n lalsuite-docs --no-deps python-ligo-lw
+    - conda activate lalsuite-docs
   script:
     - ./00boot
-    - ./configure --enable-doxygen --prefix=$(pwd)/_inst
+    - ./configure --enable-sphinx --prefix=$(pwd)/_inst
     - make -j${CPU_COUNT} install-html
     - mv _inst/share/doc html
     - cd html