Add plugin removal docs and a banner for EOL

Also removed the old survey banner.

closes #534

CHANGES/534.doc

@@ -0,0 +1,2 @@
+Added steps to remove the plugin and announced its EOL.
+Pulp-2to3-migration plugin reaches its EOL on December 31, 2022. The last supported pulpcore version is 3.19.

docs/_static/survey_banner.js → docs/_static/eol_banner.js

@@ -3,7 +3,8 @@ window.onload = function() {
     var body = document.getElementsByClassName("bodywrapper")[0]
     var doc = document.getElementsByClassName("body")[0]
     elem.className = "admonition important"
-    elem.id = "pulp-survey-banner"
-    elem.innerHTML = "<p>Please take our <a href=\"https://forms.gle/C3QwT9SVncXETipu9\">survey</a> to help us improve Pulp!</p>";
+    elem.id = "pulp-2to3-migration-eol-banner"
+    elem.innerHTML = "<p>This plugin reaches its EOL on December 31, 2022. The last supported pulpcore" +
+        " version is 3.19.</p>";
     body.insertBefore(elem, doc)
 }

docs/conf.py

@@ -103,7 +103,7 @@
 html_static_path = ['_static']
 
 # Add in a banner
-html_js_files = ['survey_banner.js']
+html_js_files = ['eol_banner.js']
 
 # Custom sidebar templates, must be a dictionary that maps document names
 # to template names.

docs/index.rst

@@ -25,6 +25,7 @@ Table of Contents
    restapi
    changes
    plugin_writers_guide
+   plugin_removal
 
 
 Indices and tables

docs/migration_plan.rst

@@ -1,5 +1,5 @@
 Migration Plan
---------------
+==============
 
 To configure what to migrate to Pulp 3, one needs to define a Migration Plan (MP).
 A MP defines which plugins to migrate and how.

docs/plugin_removal.rst

@@ -0,0 +1,49 @@
+Plugin removal
+==============
+
+When the move from Pulp 2 to Pulp 3 is done, the pulp-2to3-migration plugin is no longer needed.
+
+It is recommended to remove the plugin because:
+
+    * it will reach EOL sooner than other Pulp plugins. Having it installed will prevent the system
+      from further upgrades.
+    * it stores a lot of Pulp 2 data in the Pulp 3 database which was used during migration but is
+      no longer needed and just takes space.
+
+
+``remove-plugin`` command use
+-----------------------------
+
+In order to remove a Pulp plugin, just uninstalling it is not enough, first the ``remove-plugin``
+command should be used.
+
+    1. Stop all Pulp services.
+    2. Run the ``remove-plugin`` command.
+
+    This step ensures that all data for this plugin is properly removed from the database.
+
+    .. warning::
+
+        If this step is skipped, other plugins might not function properly (e.g. repository removal
+        will fail for the migrated repositories).
+
+    .. code-block:: bash
+
+        $ pulpcore-manager remove-plugin pulp_2to3_migration
+
+    3. Uninstall the pulp-2to3-migration plugin.
+
+    Steps to uninstall depend on how it was originally installed (usually, via ``pip`` for PyPI
+    installations or ``dnf`` for RPM installations)
+
+    .. warning::
+
+        It is very important to perform the uninstallation step for this plugin because it has
+        relations and references to other Pulp plugins. If this step is skipped, other plugins might not
+        function properly (e.g. repository removal will fail for the migrated repositories).
+
+    4. Start Pulp services.
+
+
+It is possible to install the plugin again following the standard process.
+Under the normal circumstances, there should be no need for it.