[CHORE] Add install external-secrets for helm (#1758)

### Description

- Without installing the external-secret repo for helm, the
`fake-secret-store` installation will fail.
- Add install external-secrets for helm

### Context

- document improvement

### Testing

- `./gradlew test`

Author: lijamie98

helm-charts/README.md

@@ -25,6 +25,7 @@ minikube start
 
 ```bash
 helm repo add external-secrets https://charts.external-secrets.io
+helm repo update
 helm install external-secrets \
    external-secrets/external-secrets \
     -n external-secrets \
@@ -37,6 +38,7 @@ To install `postgresql` and `postgresql-ref`, run the following commands:
 
 ```bash
 helm repo add bitnami https://charts.bitnami.com/bitnami
+helm repo update
 helm install postgresql-ref bitnami/postgresql --version 15.1.2 --set global.postgresql.auth.postgresPassword=123456789
 helm install postgresql bitnami/postgresql --version 15.1.2 --set global.postgresql.auth.postgresPassword=123456789
 ```
@@ -58,7 +60,7 @@ This should only be run one time.
 
 ```bash
 source ../.env
-helm upgrade --install fake-secret-store ./secret-store/ --set sep10_signing_seed=$SECRET_SEP10_SIGNING_SEED --set sentry_auth_token=$SENTRY_AUTH_TOKEN --set payment_signing_seed=${APP__PAYMENT_SIGNING_SEED}
+helm upgrade --install fake-secret-store ./secret-store/ --set sep10_signing_seed=$SECRET_SEP10_SIGNING_SEED --set sentry_auth_token=$SENTRY_AUTH_TOKEN --set payment_signing_seed=$APP__PAYMENT_SIGNING_SEED
 ```
 
 To show if the secret store is running, run the following command:

helm-charts/secret-store/templates/secretstore.yaml

@@ -18,7 +18,7 @@ spec:
               "SEP24_MORE_INFO_URL_JWT_SECRET": "b106cce1e32ebe342ea1e38d363fe048c7dc9c1b773658f83e22b78125785d89",
               "SEP6_MORE_INFO_URL_JWT_SECRET": "3a614cf5da456aaad61dc7532f6c422fc2b833c0c05102b47b1ac2e8f0bff2e8",
               "SEP10_JWT_SECRET": "10bb04a51338a1df86c2e807f8fe36168cf9a480d70c233452ec7e198ab33b7c",
-              "SEP10_SIGNING_SEED": {{ .Values.sep10_signing_seed }},
+              "SEP10_SIGNING_SEED": "{{ .Values.sep10_signing_seed }}",
               "EVENTS_QUEUE_KAFKA_USERNAME": "user1",
               "EVENTS_QUEUE_KAFKA_PASSWORD": "123456789",
               "SENTRY_AUTH_TOKEN": {{ default "\"\"" .Values.sentry_auth_token }}
@@ -28,7 +28,7 @@ spec:
             {
               "POSTGRES_USER": "postgres",
               "POSTGRES_PASSWORD": "123456789",
-              "PAYMENT_SIGNING_SEED": {{ .Values.payment_signing_seed }},
+              "PAYMENT_SIGNING_SEED": "{{ .Values.payment_signing_seed }}",
               "SEP24_INTERACTIVE_JWT_KEY": "c5457e3a349df9002117543efa7e316dd89e666a5ce6f33a0deb13e90f3f1e9d",
               "PLATFORM_ANCHOR_SECRET": "myPlatformToAnchorSecret",
               "ANCHOR_PLATFORM_SECRET": "myAnchorToPlatformSecret",