viessmann charger api: first draft for a template...

... mostly just looking for some feedback.
Based on the api investigation at evcc-io#19639 (comment)

* why does `getmode` trigger two identical http requests?
* authentication via oauth2 using only the viessmann client id
* user guidance to figure out the installation id, gateway serial and device id
* should/can we configure a longer interval between updates? If so, how? Viessmann has an api limit of ~1 request per minute

```
chargers:
  - name: viessmann
    type: template
    template: viessmann
    installation_id: 23XXXXX          # all digits
    gateway_serial: 76XXXXXXXXXXXXXX  # all digits
    device_id: 0
    target_temperature: 47
    token: eyJ.....
```

```
./evcc --log trace -c ~/.evcc/evcc.yaml --database ~/.evcc/evcc.db charger viessmann
...
[viessmann] TRACE 2025/03/25 19:35:15 GET https://api.viessmann.com/iot/v2/features/installations/23XXXXX/gateways/76XXXXXXXXXXXXXX/devices/0/features/heating.dhw.oneTimeCharge
[viessmann] TRACE 2025/03/25 19:35:16 {
  "data": {
    ...
  }
}
[viessmann] TRACE 2025/03/25 19:35:16 GET https://api.viessmann.com/iot/v2/features/installations/23XXXXX/gateways/76XXXXXXXXXXXXXX/devices/0/features/heating.dhw.oneTimeCharge
[viessmann] TRACE 2025/03/25 19:35:16 {
  "data": {
    ...
  }
}
...
Charge status: B
Enabled:       false
Features:      [Heating IntegratedDevice]
```

```
./evcc --log trace -c ~/.evcc/evcc.yaml --database ~/.evcc/evcc.db charger viessmann --enable
[viessmann] TRACE 2025/03/25 13:28:51 {"temperature": 47}
--
{
  "data": {
    "success": true,
    "message": null,
    "reason": "COMMAND_EXECUTION_SUCCESS"
  }
}
[viessmann] TRACE 2025/03/25 13:28:52 { }
--
{
  "data": {
    "success": true,
    "message": null,
    "reason": "COMMAND_EXECUTION_SUCCESS"
  }
}

```

```
./evcc --log trace -c ~/.evcc/evcc.yaml --database ~/.evcc/evcc.db charger viessmann --disable
--
{
  "data": {
    "success": true,
    "message": null,
    "reason": "COMMAND_EXECUTION_SUCCESS"
  }
}
```

Author: mpollmeier

Diff for: templates/definition/charger/viessmann.yaml

@@ -0,0 +1,64 @@
+template: viessmann
+products:
+  - brand: Viessmann
+    description:
+      generic: Viessmann (SG Ready)
+group: heating
+# requirements:
+#   evcc: ["sponsorship"]
+params:
+  # TODO mark parameters as required
+  - name: installation_id  # TODO guide user on how to get this value
+  - name: gateway_serial   # TODO guide user on how to get this value
+  - name: device_id        # TODO guide user on how to get this value
+  - name: token            # TODO get with client id via oauth2
+  - name: target_temperature
+    description:
+      de: Zieltemperatur für Einmal-Warmwasser-Zubereitung (°C), max=60
+      en: Target temperator for onetimecharge (°C), max=60
+    default: 45
+    type: int
+render: |
+  type: sgready
+  getmode:
+    source: http
+    uri: https://api.viessmann.com/iot/v2/features/installations/{{.installation_id}}/gateways/{{.gateway_serial}}/devices/{{.device_id}}/features/heating.dhw.oneTimeCharge
+    headers:  
+      - content-type: application/json
+      - authorization: Bearer {{.token}}
+    jq: '.data.properties.active.value | if . == false then 1 elif . == true then 2 else . end'
+    # false -> oneTimeCharge is disabled -> normal mode -> 1
+    # true -> oneTimeCharge is enabled -> boost mode -> 2
+  setmode:
+    source: switch
+    switch:
+    - case: 1 # normal
+      set:
+        source: http
+        uri: https://api.viessmann.com/iot/v2/features/installations/{{.installation_id}}/gateways/{{.gateway_serial}}/devices/{{.device_id}}/features/heating.dhw.oneTimeCharge/commands/deactivate
+        method: POST 
+        headers:  
+          - content-type: application/json
+          - authorization: Bearer {{.token}}
+        body: >
+          { }
+    - case: 2 # boost
+      set:
+        source: sequence
+        set:
+        - source: http
+          uri: https://api.viessmann.com/iot/v2/features/installations/{{.installation_id}}/gateways/{{.gateway_serial}}/devices/{{.device_id}}/features/heating.dhw.temperature.temp2/commands/setTargetTemperature
+          method: POST
+          headers:  
+            - content-type: application/json
+            - authorization: Bearer {{.token}}
+          body: >
+            {"temperature": {{.target_temperature}}}
+        - source: http
+          uri: https://api.viessmann.com/iot/v2/features/installations/{{.installation_id}}/gateways/{{.gateway_serial}}/devices/{{.device_id}}/features/heating.dhw.oneTimeCharge/commands/activate
+          method: POST 
+          headers:  
+            - content-type: application/json
+            - authorization: Bearer {{.token}}
+          body: >
+            { }