docs(wiki): Migration System page

wiki/Behavior.md

@@ -1,11 +1,11 @@
 Special notes about behavior of Recyclarr with regards to the various services it supports will be
 documented here.
 
-# Sonarr
+## Sonarr
 
 Each section below represents a topic covering certain behavior relevant to Sonarr.
 
-## Release Profile Naming
+### Release Profile Naming
 
 The script procedurally generates a name for release profiles it creates. For the following example:
 
@@ -20,3 +20,9 @@ The name is generated as follows:
    created (which Recyclarr will not touch).
 - `Anime - First Release Profile` is the name of the Release Profile (taken from the `name` property
   of its corresponding JSON file).
+
+### Migration System
+
+See the [Migration System] page.
+
+[Migration System]: https://github.com/rcdailey/recyclarr/wiki/Migration-System

wiki/Migration-System.md

@@ -0,0 +1,54 @@
+The Migration System allows Recyclarr to attempt certain automatic actions for the user. These
+actions, referred to as Migration Steps, are usually in response to certain changes between releases
+of Recyclarr (mostly major releases, which represent breaking changes). The overall goal of this
+system is to reduce the amount of manual action a user must take.
+
+## Behavior
+
+1. When Recyclarr is executed, it first runs through all of the Migration Steps in a specific,
+   pre-determined order.
+1. Each Migration Step is checked if it needs to run or not.
+   - If it needs to run, its actions are performed immediately.
+   - Otherwise, it is skipped and the next Migration Step is processed.
+
+Migration Steps can fail. When this happens, instructions are provided to the user on how to recover
+and/or perform those steps manually. Regardless of the reason, Recyclarr will immediately exit and
+cannot proceed until the advice output during the previous execution is followed.
+
+## Failure & Recovery
+
+When a Migration Step fails, processing of further steps is halted and the program exits. The
+failure also results in diagnostic information and remediation steps being printed to the console:
+
+- A description of the Migration Step that failed. This is usually a description of what the step
+  was trying to do.
+- A failure reason. Explains why the step failed and could not be processed.
+- Remediation steps. One or more ways to solve the problem. Will likely either ask you to perform
+  the steps by hand or take some action to allow the migration step to succeed the next time
+  Recyclarr is executed.
+
+## Current Migration Steps
+
+The list below describes the migration steps that are performed today, under what conditions they
+will be executed, and reasons why they might fail. Most of this information is already printed in
+real time by Recyclarr in response to failures.
+
+### Rename app data directory from `trash-updater` to `recyclarr`
+
+- **When**: `v2.0`
+- **What**: Renames your `trash-updater` app data directory to `recyclarr` automatically.
+- **Why**: The application was renamed from Trash Updater to Recyclarr. Thus, the app data directory
+  name needed to follow suit.
+- **How can it fail?**
+  - The `recyclarr` directory already exists.
+  - User lacks sufficient permissions on the filesystem.
+
+### Rename default `trash.yml` file to `recyclarr.yml`
+
+- **When**: `v2.0`
+- **What**: Renames your `trash.yml` file to `recyclarr.yml` automatically.
+- **Why**: The application was renamed from Trash Updater to Recyclarr. Thus, the app data directory
+  name needed to follow suit.
+- **How can it fail?**
+  - The `recyclarr.yml` file already exists.
+  - User lacks sufficient permissions on the filesystem.

wiki/Upgrade-Guide.md

@@ -79,8 +79,13 @@ release_profiles:
       - tv
 ```
 
-In this release, since you now have the ability to specifically include optionals that you want, I
-recommend visiting the [Configuration Reference] and learning more about the `include` and `exclude`
-filter lists.
+## Other Notes
+
+- In this release, since you now have the ability to specifically include optionals that you want, I
+  recommend visiting the [Configuration Reference] and learning more about the `include` and
+  `exclude` filter lists.
+- Migration steps have been added. See the `v2.0` migration steps documented on the [Migration
+  System] page.
 
 [Configuration Reference]: https://github.com/rcdailey/recyclarr/wiki/Configuration-Reference
+[Migration System]: https://github.com/rcdailey/recyclarr/wiki/Migration-System