Create a readme for developers in .devcontainer

.devcontainer/README.md

+# `ngx_http_voms_module` for developers
+
+A devcontainer is ready to use for the developers. A set of packages without nginx are already installed.
+
+## How to build and install nginx with or without httpg patch
+
+To build and install the last stable version of [nginx](http://nginx.org/en/download.html) (1.22.1) you have to copy the ```nginx.repo``` file (it is contained in the ```docker``` directory) into the ```/etc/yum.repos.d/``` directory and install nginx with yum:
+
+```
+$ sudo cp docker/nginx.repo /etc/yum.repos.d/
+$ sudo yum install -y nginx
+```
+
+Otherwise, if you want to build and install the last stable version of [nginx](http://nginx.org/en/download.html) (1.22.1) with the httpg patch, a bash library is ready to use. You can source it and follow the commands below:
+
+```
+$ source .devcontainer/assets/build-library.sh
+$ downloadNginx
+$ buildHttpgNginxRPM
+$ sudo rpm -ivh ~/rpmbuild/RPMS/x86_64/nginx-httpg-1.22.1-1.el7.ngx.x86_64.rpm
+```
+
+## How to build and install the `ngx_http_voms_module`
+
+If you want to build and install the `ngx_http_voms_module`, nginx have to be installed in the container (see the previous section). When this requirement is satisfied, you can use the library contained in the ```.devcontainer/assets``` folder as follows (NOTE: if you have already download nginx source file, you can skip the relative command):
+
+```
+$ source .devcontainer/assets/build-library.sh
+$ downloadNginx
+$ buildVomsModuleRPM
+$ sudo rpm -ivh ~/rpmbuild/RPMS/x86_64/nginx-module-http-voms-1.22.1-1.el7.x86_64.rpm
+```

.devcontainer/assets/build-library.sh

+#!/usr/bin/env bash
+
+# Copyright 2018-2023 Istituto Nazionale di Fisica Nucleare
+# SPDX-License-Identifier: EUPL-1.2
+
+downloadNginx() {
+
+# check if a version of nginx is specified
+if [ -z ${ngxVersion} ]; then
+    ngxVersion=1.22.1
+fi
+echo "nginx version required: ${ngxVersion}";
+
+# check if ~/rpmbuild exists and is not empty
+if [ "$(ls -A ${HOME}/rpmbuild)" ];
+then
+    echo "Error: ${HOME}/rpmbuild already exists and is not empty"
+    return 1
+fi
+
+# setup rpmbuild dir
+cat <<EOF > ${HOME}/.rpmmacros
+%_topdir %{getenv:HOME}/rpmbuild
+EOF
+cd
+rpmdev-setuptree
+
+# download nginx sources
+cd ~/rpmbuild/SOURCES/
+wget http://nginx.org/packages/centos/7/SRPMS/nginx-$ngxVersion-1.el7.ngx.src.rpm
+rpm2cpio nginx-$ngxVersion-1.el7.ngx.src.rpm | cpio -idm
+
+cd /workspaces/ngx_http_voms_module
+
+}
+
+buildHttpgNginxRPM() {
+
+if [ -z ${CI_PROJECT_DIR} ]; then
+    CI_PROJECT_DIR="/workspaces/ngx_http_voms_module";
+fi
+
+# set the nginx spec file with the httpg patch
+cd ~/rpmbuild/SOURCES/
+cp ${CI_PROJECT_DIR}/nginx-httpg_no_delegation.patch ${HOME}/rpmbuild/SOURCES/
+cp ${CI_PROJECT_DIR}/rpm/nginx.spec ~/rpmbuild/SPECS
+
+# build rpm
+rpmlint ~/rpmbuild/SPECS/nginx.spec
+rpmbuild -ba ~/rpmbuild/SPECS/nginx.spec
+
+# include httpg in the rpm name
+mv ~/rpmbuild/RPMS/x86_64/nginx-$ngxVersion-1.el7.ngx.x86_64.rpm  ~/rpmbuild/RPMS/x86_64/nginx-httpg-$ngxVersion-1.el7.ngx.x86_64.rpm
+mv ~/rpmbuild/RPMS/x86_64/nginx-debuginfo-$ngxVersion-1.el7.ngx.x86_64.rpm  ~/rpmbuild/RPMS/x86_64/nginx-httpg-debuginfo-$ngxVersion-1.el7.ngx.x86_64.rpm
+mv ~/rpmbuild/SRPMS/nginx-$ngxVersion-1.el7.ngx.src.rpm  ~/rpmbuild/SRPMS/nginx-httpg-$ngxVersion-1.el7.ngx.src.rpm
+
+cd ${CI_PROJECT_DIR}
+
+}
+
+buildVomsModuleRPM() {
+
+if [ -z ${CI_PROJECT_DIR} ]; then
+    CI_PROJECT_DIR="/workspaces/ngx_http_voms_module";
+fi
+
+# set voms modules sources
+cd ~/rpmbuild/SOURCES/
+mkdir ngx-http-voms-module
+cp ${CI_PROJECT_DIR}/config ngx-http-voms-module/
+cp ${CI_PROJECT_DIR}/config.make ngx-http-voms-module/
+cp -r ${CI_PROJECT_DIR}/src ngx-http-voms-module/
+cp ${CI_PROJECT_DIR}/rpm/nginx-module-http-voms.spec ~/rpmbuild/SPECS
+
+# build rpm
+rpmlint ~/rpmbuild/SPECS/nginx-module-http-voms.spec
+rpmbuild -ba ~/rpmbuild/SPECS/nginx-module-http-voms.spec
+
+cd ${CI_PROJECT_DIR}
+
+}