Merge branch 'add-kamailio-package' into 'master'

Add kamailio package

See merge request !180

charm-packages/kamailio/kamailio_knf/juju-bundles/bundle.yaml

+bundle: kubernetes
+applications:
+  kamailio:
+    charm: ./kamailio-k8s_ubuntu-20.04-amd64.charm
+    scale: 1
+    trust: true
+    options:
+      sip-domain: localhost
+    resources:
+      kamailio-image: kamailio/kamailio:5.3.3-stretch
+  sipp:
+    charm: ./sipp-k8s_ubuntu-20.04-amd64.charm
+    scale: 1
+    trust: true
+    options:
+    resources:
+      sipp-image: grigiu/sipp:latest

charm-packages/kamailio/kamailio_knf/kamailio_cnfd.yaml

+vnfd:
+  id: kamailio_cnf
+  product-name: kamailio_cnf
+  mgmt-cp: mgmt-ext
+  k8s-cluster:
+    nets:
+      - id: mgmtnet
+  ext-cpd:
+    - id: mgmt-ext
+      k8s-cluster-net: mgmtnet
+  kdu:
+    - name: kamailio-kdu
+      juju-bundle: bundle.yaml
+  df:
+    - id: default-df
+      lcm-operations-configuration:
+        operate-vnf-op-config:
+          day1-2:
+            - id: kamailio-kdu
+              config-primitive:
+                - name: options
+                  parameter:
+                    - name: application-name
+                      data-type: STRING
+                      default-value: sipp
+                    - name: ip
+                      data-type: STRING
+                    - name: port
+                      data-type: INTEGER
+                      default-value: 5060
+                - name: restart
+                  parameter:
+                    - name: application-name
+                      data-type: STRING
+                      default-value: kamailio
+                - name: start
+                  parameter:
+                    - name: application-name
+                      data-type: STRING
+                      default-value: kamailio
+                - name: stop
+                  parameter:
+                    - name: application-name
+                      data-type: STRING
+                      default-value: kamailio

charm-packages/kamailio/kamailio_ns/kamailio_nsd.yaml

+nsd:
+  nsd:
+    - id: kamailio_ns
+      name: kamailio_ns
+      version: "1.0"
+      description: Kamailio Server and Sipp Client
+      vnfd-id:
+        - kamailio_cnf
+      virtual-link-desc:
+        - id: mgmtnet
+          mgmt-network: true
+      df:
+        - id: default-df
+          vnf-profile:
+            - id: kamailio
+              vnfd-id: kamailio_cnf
+              virtual-link-connectivity:
+                - virtual-link-profile-id: mgmtnet
+                  constituent-cpd-id:
+                    - constituent-base-element-id: kamailio
+                      constituent-cpd-id: mgmt-ext