added migration checklist

sapphire_hardware_migration_checklist.md

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+## Sapphire Migration Checklist
+
+### Meta
+
+  - Migrate stagingsapphire to new hardware (following the procedure below)
+  - Migrate stagingsapphire with dump from sapphire
+  - Migrate sapphire to new hardware (following the procedure below)
+  - Drop databases on stagingsapphire and initialize with dummy data through rake task.
+
+### Webserver
+
+  - switch to nginx
+  - ssl certs (?)
+  - new.sapphire.isds.tugraz.at
+  - https://www.phusionpassenger.com/docs/advanced_guides/install_and_upgrade/nginx/install/oss/el8.html14:37
+
+### Questions (for Matthias and/or Helmut)
+
+  - CentOS 8 Stream is a rolling release? Are there and implications for sapphire because of some security critical OS updates we will have to do?
+    (website reads: "**Continuously delivered** distro ...[https://www.centos.org/centos-stream/])
+    - How are package updates going to be handled?
+
+### Prerequisites
+
+  - create production db dump
+  - **copy** assets to new hardware
+
+### Install
+
+  - Database: PostgreSQL 8.4.20 -> probs to 13.xx.xx
+  - Ruby (install via rbenv -> 2.6.5p114 (2019-10-01 revision 67812)) -> 2.7.xx
+    - https://medium.com/@adrienjarthon/ruby-jemalloc-results-for-updown-io-d3fb2d32f67f
+  - Redis (Redis server v=3.2.12 sha=00000000:0 malloc=jemalloc-3.6.0 bits=64 build=b2d74fe5fff7657d) -> 6.2.5
+  - NodeJS (v0.10.35) -> ??
+  - Bundler
+  - Cap Deploy (check deploy target)
+
+### Setup
+
+  - setup config files:
+    - database.yml
+    - mail.yml
+    - secrets.yml
+    - sidekiq.yml
+  - gem install bundler
+  - import DB dump (lookup for appropriate GIST/snippet TODO)
+  - check if assets are correctly linked (i.e. in the correct folder, is this sufficient?)
+
+### Checks
+
+  - check certificate
+  - check auto https
+  - check mailing
+  - check upload (tests sidekiq)
+  - check entering of new ratings (tests redis)