Short readme about how to use the service (tried to not be too wordy

shared/workspaces/workspaces/system/README.md

+# CASA Version Matrix Service
+The CASA version matrix is responsible for returning valid CASA + pipeline versions for processing as well as
+maintaining our lists of installed and allowed versions for various capabilities.
+
+## Getting valid versions
+Each capability has a list of CASA versions that are tested and verified for use. These allowed versions are
+cross-referenced against the installed versions in `/home/ssa/casa/` to get a full list of versions that are allowed for
+processing with the given capability.
+
+Examples of using the service to get a single version or a list of versions (the version name(s) and full path(s) are
+in the response body):
+```python
+import requests
+prefix = 'http://capability:3457/casa_matrix/'
+
+# Single version (telescope optional), gives the preferred version from CAPO
+r = requests.get(prefix + 'version', json={'capability': 'restore_cms', 'telescope': 'alma'})
+print(r.json())
+
+# Single version, returns the given version if it's valid
+r = requests.get(prefix + 'version', json={'version': '6.4.1-12|2022.2.0.68'})
+print(r.json())
+
+# List of versions with the preferred version first in the list
+r = requests.get(prefix + 'versions', json={'capability': 'restore_cms'})
+print(r.json())
+```
+
+## Getting CASA recipes
+Each capability has a `casa_recipe` field that can be obtained via the service.
+
+Example:
+```python
+import requests
+prefix = 'http://capability:3457/casa_matrix/'
+r = requests.get(prefix + 'recipe', json={'capability': 'restore_cms'})
+print(r.json())
+```
+
+
+## Refreshing installed versions
+We maintain a list of symlinks to usable CASA + pipeline versions to filter out CASA packages that do not have a
+corresponding pipeline. Our symlinks are in `/home/ssa/casa/` and link to CASA's managed installations in
+`/home/casa/packages`. It is recommended to point all WS activities (e.g. workflows, capabilities) to our managed
+symlinks.
+
+Example of using the service to refresh the installed version links:
+```python
+import requests
+requests.post('http://capability:3457/casa_matrix/links')
+```
+
+## Managing allowed versions
+Each capability has a list of CASA versions that are allowed for processing. These are maintained in the `casa_matrix_*`
+DB tables.
+
+Examples of using the service to add/update/delete versions from the tables:
+
+```python
+import requests
+url = 'http://capability:3457/casa_matrix/db/version'
+
+# Add
+requests.post(url, json={'version': '2.2.2', 'is_cluster_compatible': False, 'capabilities': ['curator', 'download']})
+
+# Update
+requests.put(url, json={'version': '2.2.2', 'is_cluster_compatible': True, 'capabilities': ['restore_cms', 'std_cms_imaging']})
+
+# Delete
+requests.delete(url, json={'version': '2.2.2'})
+```