Add a little tutorial for how to configure protections. (#43)

the-draupnir-project/planning#18.

docs/protections/configuring-protections.md

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+---
+sidebar_position: 1
+---
+
+# Configuring protections
+
+This is a tutorial that aims to guide a moderator through configuring
+a protection. We use the `JoinWaveShortCircuitProtection` in the
+examples, but the steps are the same for every protection.
+
+## Displaying the protection settings
+
+Each protection can provide different configuration options, which are
+sometimes also referred to as _protection settings_. The command that
+is used to view these settings
+
+To display an overview for a protection's protection settings, you can
+use the `!draupnir protections show <protection name>` command. If you
+don't know the name of the protection that you are trying to find, you
+can copy the name from the list provided when using the `!draupnir
+protections` command.
+
+So for the `JoinWaveShortCircuitProtection`, the command would look
+like this:
+
+`!draupnir protections show JoinWaveShortCircuitProtection`:
+
+**Protection Settings**
+
+- `maxPer`: The maximum number of users that can join a room in the
+  timescaleMinutes timescale before the room is set to invite-only.
+  default value: 50 (number)
+
+- `timescaleMinutes`: The timescale in minutes over which the maxPer
+  users can join before the room is set to invite-only.
+
+As you can see, we are provided with a short description of each
+setting, and the setting's name that we can copy into a command.
+
+## Changing protection settings
+
+Let's consider adjusting the protection settings for the
+`JoinWaveShortCircuitProtection`. If we have a particularly inactive
+room, we might want to reduce the timesacale and the maximum number of
+joins within it a little.
+
+To do this, we can use the `!draupnir protections config set
+<protection name> <property name>` command.
+
+`!draupnir protections config set JoinWaveShortCircuitProtection
+maxPer 5` would set the `maxPer` setting to just 5 joins. And
+`!draupnir protections config set JoinWaveShortCircuitProtection
+timescaleMinutes 10` would make sure that a maximum of 5 joins is
+allowed over a period of 10 minutes before triggering the short
+circuit.
+
+### Managing sets
+
+Some protections have settings that are a set of values. The
+`TrustedReporters` protection has a setting like this.
+
+- `mxids`: The users who are marked as trusted reporters. default
+  value: [] (empty array)
+
+To manage the list, we can use the `!draupnir protections config <add/remove> <protection name> <property name>` command.
+
+So to add a user to the list of trusted reporters, we would use
+`!draupnir protections config add TrustedReporters mxids
+@alice:example.com`, and to remove a user `!draupnir protections
+config remove TrustedReporters mxids @alice:example.com`.