Add JFrog Artifactory and Sonatype Nexus integrations documentation

[tdruez]

Issue: #1725 #1739

Changes:

• Add JFrog Artifactory integration documentation
• Add Sonatype Nexus integration documentation

[tdruez]

New documentation available at https://scancodeio.readthedocs.io/en/latest/inputs.html#jfrog-artifactory and https://scancodeio.readthedocs.io/en/latest/inputs.html#sonatype-nexus

JFrog Artifactory
-----------------

ScanCode.io can fetch artifacts from **JFrog Artifactory** repositories using
standard download URLs.

The URL format follows Artifactory's REST API pattern::

    https://<artifactory-host>/artifactory/<repo-key>/<artifact-path>

Example::

    https://mycompany.jfrog.io/artifactory/libs-release/org/apache/commons/commons-lang3/3.12.0/commons-lang3-3.12.0.jar

For **authentication**, configure credentials in your ``.env`` file using one of
these methods:

Using Basic Authentication::

    SCANCODEIO_FETCH_BASIC_AUTH="mycompany.jfrog.io=username,password"

Using API Key (via headers)::

    SCANCODEIO_FETCH_HEADERS="mycompany.jfrog.io=X-JFrog-Art-Api=<YOUR_API_KEY>"

Using Access Token::

    SCANCODEIO_FETCH_HEADERS="mycompany.jfrog.io=Authorization=Bearer <YOUR_TOKEN>"

.. tip::
    You can also use a :ref:`.netrc file <scancodeio_settings_netrc_location>` for
    authentication if your organization already maintains one.

.. _inputs_nexus:

Sonatype Nexus
--------------

ScanCode.io can fetch artifacts from **Sonatype Nexus Repository** (versions 2 and 3)
using standard download URLs.

For **Nexus 3**, the URL format follows the repository path pattern::

    https://<nexus-host>/repository/<repo-name>/<path-to-artifact>

Example for a Maven artifact::

    https://nexus.mycompany.com/repository/maven-central/ch/qos/logback/logback-core/1.4.0/logback-core-1.4.0.jar

Example for a PyPI package::

    https://nexus.mycompany.com/repository/pypi-proxy/packages/urllib3/1.26.7/urllib3-1.26.7-py2.py3-none-any.whl

Example for an npm package::

    https://nexus.mycompany.com/repository/npm-proxy/redis/-/redis-2.8.0.tgz

For **authentication**, configure credentials in your ``.env`` file:

Using Basic Authentication::

    SCANCODEIO_FETCH_BASIC_AUTH="nexus.mycompany.com=username,password"

Using a Bearer Token::

    SCANCODEIO_FETCH_HEADERS="nexus.mycompany.com=Authorization=Bearer <YOUR_TOKEN>"

.. tip::
    You can also use a :ref:`.netrc file <scancodeio_settings_netrc_location>` for
    authentication if your organization already maintains one.