Add local development network morph/nix configuration

Builds on and requires !81 (merged).

---

This adds morph/nix config that one can morph build; morph push; morph deploy after having called vagrant up from !81 (merged).

Note that a bit of configuration to make the our software in the VMs actually work is still missing. For example the ZKAP issuer isn't starting with propers keys.

Refers https://whetstone.privatestorage.io/privatestorage/privatestorageops/-/issues/317

morph/grid/local/README.rst

@@ -36,13 +36,35 @@ If you run an older Nixpkgs, retrieve and use the latest Vagrant development ver
 Use the local development environment
 `````````````````````````````````````
 
-Build and start the VMs::
+1. Build and start the VMs::
 
-  VAGRANT_DEFAULT_PROVIDER=virtualbox vagrant up
+    VAGRANT_DEFAULT_PROVIDER=virtualbox vagrant up
 
-Then::
+2. Then, once::
 
-  morph build grid.nix
-  morph push grid.nix
-  morph deploy grid.nix switch
+    vagrant ssh-config > ./vagrant-ssh-config
+
+3. Edit the output: Add the IPs from ``grid.nix`` to the ``vagrant-ssh-config`` **Host match blocks** so the config reads like::
+
+    Host payments1 192.168.67.21
+      HostName 192.168.67.21
+      User vagrant
+      Port 22
+      [...]
+
+4.  Then, make morph use this ssh config either - with newer morph [#]_ - by pointing it to it::
+
+     export SSH_CONFIG_FILE=./vagrant-ssh-config
+
+  Or, with older morph, adding the config to your user's ``~/.ssh/config`` file.
+
+  .. [#]  Morph honors the ``SSH_CONFIG_FILE`` environment variable `since 3f90aa88 (March 2020, v 1.5.0) <https://github.com/DBCDK/morph/commit/3f90aa885fac1c29fce9242452fa7c0c505744ef#diff-d155ad793bd62e6ea4c44ba985049ecb13a4f4f32f799791b2bce695a16c0101>`_.
+
+5. Then, build and deploy our software to the Vagrant VMs::
+
+    morph build grid.nix
+    morph push grid.nix
+    morph deploy grid.nix switch
+
+  You will now be able to log in with the users and keys you set in your ``localdev-users.nix`` file.