docs: Add 1.2.0 release note.

release-notes.1.2.0.md

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+# vspd 1.2.0
+
+vspd v1.2.0 contains all development work completed since v1.1.0 (March 2022).
+Since then, 80 commits have been produced and merged by 3 contributors.
+All commits included in this release can be viewed on GitHub
+[here](https://github.com/decred/vspd/compare/release-v1.1.0...release-v1.2.0).
+
+## Dependencies
+
+vspd 1.2.0 must be built with go 1.19 or later, and requires:
+
+- dcrd 1.8.0
+- dcrwallet 1.8.0
+
+When deploying vspd to production, always use release versions of all binaries.
+Neither vspd nor its dependencies should be built from master when handling
+mainnet tickets.
+
+## Recommended Upgrade Path
+
+The upgrade path below includes vspd downtime, during which clients will not be
+able to register new tickets, check their ticket status, or update their voting
+preferences. Voting on tickets already registered with the VSP will not be
+interrupted. You may wish to put up a temporary maintenance webpage or announce
+downtime in public channels.
+
+1. Build vspd from the 1.2.0 release tag. Build dcrwallet and dcrd from their
+   1.8.0 release tags.
+1. Stop vspd.
+1. Stop the instance of dcrd running on the vspd server.
+1. **Make a backup of the vspd database file in case rollback is required.**
+1. Install new dcrd binary on the vspd server and start it to begin database
+   upgrades. You can proceed with the following steps while the upgrades run.
+1. Upgrade voting wallets one at a time so at least two wallets remain online
+   for voting. On each server:
+    1. Stop dcrwallet.
+    1. Stop dcrd.
+    1. Install new dcrd binary and start.
+    1. Wait for dcrd database upgrades to complete.
+    1. Check dcrd log file for warnings or errors.
+    1. Install new dcrwallet binary and start.
+    1. Wait for dcrwallet database upgrades to complete.
+    1. Check dcrwallet log file for warnings or errors.
+1. Wait for dcrd on the vspd server to complete its database upgrade.
+1. Check dcrd log file for warnings or errors.
+1. Install new vspd binary and start it.
+1. Check vspd log file for warnings or errors.
+1. Log in to the admin webpage and check the VSP Status tab for any issues.
+
+## Notable Changes
+
+- vspd has moved into the cmd directory of the repo. This is standard practise
+  in Decred repos which include more than one golang executable. The new command
+  to build is:
+
+  ```no-highlight
+  go build ./cmd/vspd
+  ```
+
+- `/vspinfo` now returns `votingwalletsonline` and `votingwalletstotal`.
+- The login form for the admin page is now limited to 3 attempts per second per IP.
+- A warning is logged when running a pre-release version of vspd on mainnet.
+- The ID of the git commit vspd was built from is now included in startup
+  logging and in the output of `--version`.
+- A new executable `vote-validator` is a tool for VSP admins to verify that
+  their vspd deployment is voting correctly according to user preferences.
+  Further details can be found in the [README](./cmd/vote-validator).
+- A new executable `v3tool` is a development tool helpful for testing changes to
+  vspd. Further details can be found in the [README](./cmd/v3tool).