WIP: implement data model as in diagram

this doesn't update the tests yet because we don't have all the data
types in place anyway yet, and I still need to come up with testable examples.

deployment/data-model.nix

@@ -85,13 +85,29 @@ in
         };
       };
     };
-    deployments = mkOption {
-      description = "Deployment of a configuration of applications to a run-time environment";
-      type = attrsOf deployment;
-    };
-    migrations = mkOption {
-      description = "Migrations from Fediversity deployments to Fediversity run-time environments";
-      type = attrsOf migration;
+    environments = mkOption {
+      description = "Run-time environments for Fediversity applications to be deployed to";
+      type = attrsOf (
+        submodule (environment: {
+          _class = "fediversity-environment";
+          options = {
+            resources = mkOption {
+              description = "Resources made available by the hosting provider";
+              type = attrsOf (
+                attrTag (
+                  lib.mapAttrs' (name: resource: {
+                    ${name} = mkOption { type = resource.provider; };
+                  }) config.resources
+                )
+              );
+            };
+            resource-mapping = mkOption {
+              description = "Mapping of resources required by applications to available resources; the result can be deployed";
+              # TODO: type = consumer-resources /* same as the output of application.config-mapping, should be in a `let` */ -> nixops4Deployment
+            };
+          };
+        })
+      );
     };
   };
 }