feat(settings): set the Google Maps key through PLACES_API_KEY

The server already put PLACES_API_KEY ahead of the key saved in the admin
panel, but nothing said so: the variable was in no template and the admin
field kept showing a stored value that no search used.

GET /me/settings now answers env_keys, the variable behind each key the
environment sets (Google, Unsplash, Amap), and null for that key's value.
The admin field turns read-only and names the variable, Test still probes
the key a search resolves to, and a save leaves those names out so the
stored fallback survives. The variable is documented in .env.example,
docker-compose.yml, the Helm chart (as a secret) and the wiki.

Addresses discussion #1881.

charts/trek/templates/deployment.yaml

@@ -75,6 +75,12 @@ spec:
                   name: {{ default (printf "%s-secret" (include "trek.fullname" .)) .Values.existingSecret }}
                   key: UNSPLASH_ACCESS_KEY
                   optional: true
+            - name: PLACES_API_KEY
+              valueFrom:
+                secretKeyRef:
+                  name: {{ default (printf "%s-secret" (include "trek.fullname" .)) .Values.existingSecret }}
+                  key: PLACES_API_KEY
+                  optional: true
             - name: AMAP_API_KEY
               valueFrom:
                 secretKeyRef:

charts/trek/templates/secret.yaml

@@ -20,6 +20,9 @@ data:
   {{- if .Values.secretEnv.UNSPLASH_ACCESS_KEY }}
   UNSPLASH_ACCESS_KEY: {{ .Values.secretEnv.UNSPLASH_ACCESS_KEY | b64enc | quote }}
   {{- end }}
+  {{- if .Values.secretEnv.PLACES_API_KEY }}
+  PLACES_API_KEY: {{ .Values.secretEnv.PLACES_API_KEY | b64enc | quote }}
+  {{- end }}
   {{- if .Values.secretEnv.AMAP_API_KEY }}
   AMAP_API_KEY: {{ .Values.secretEnv.AMAP_API_KEY | b64enc | quote }}
   {{- end }}
@@ -56,6 +59,9 @@ stringData:
   {{- if .Values.secretEnv.UNSPLASH_ACCESS_KEY }}
   UNSPLASH_ACCESS_KEY: {{ .Values.secretEnv.UNSPLASH_ACCESS_KEY }}
   {{- end }}
+  {{- if .Values.secretEnv.PLACES_API_KEY }}
+  PLACES_API_KEY: {{ .Values.secretEnv.PLACES_API_KEY }}
+  {{- end }}
   {{- if .Values.secretEnv.AMAP_API_KEY }}
   AMAP_API_KEY: {{ .Values.secretEnv.AMAP_API_KEY }}
   {{- end }}

charts/trek/values.yaml

@@ -133,6 +133,11 @@ secretEnv:
   # Get a free key at https://unsplash.com/developers. Can also be set per-admin
   # in Admin > Settings; this value overrides that. Leave empty to disable.
   UNSPLASH_ACCESS_KEY: ""
+  # Optional Google Maps API key (Places API (New) enabled) for place search, photos,
+  # details and Google transit. Overrides the key set in Admin > Settings > API Keys,
+  # whose field then shows this variable read-only. Leave empty to use the key from the
+  # admin panel, or none.
+  PLACES_API_KEY: ""
   # Optional Amap (高德地图) Web 服务 key for place search and geocoding inside mainland
   # China. Overrides the key set in Admin > Settings > API Keys. A Web 端 (JS API) key is
   # a different credential and is rejected with INVALID_USER_KEY. Leave empty to use the