Support pod.spec.containers.securityContext specification

This PR attempts to close trinodb#116

Following [the valeriano-manassero's implementation](https://github.com/valeriano-manassero/helm-charts/blob/6382a14272927a908bc006d0f1370ba9dffc821f/valeriano-manassero/trino/values.yaml#L467-L471)

let me support `pod.spec.containers.securityContext`  specification

charts/trino/README.md

@@ -244,6 +244,15 @@ Fast distributed SQL query engine for big data analytics that helps you explore
   ```
 * `securityContext.runAsUser` - int, default: `1000`
 * `securityContext.runAsGroup` - int, default: `1000`
+* `containerSecurityContext` - object, default: `{"allowPrivilegeEscalation":false,"capabilities":{"drop":["ALL"]}}`  
+
+  [Container security context](https://kubernetes.io/docs/tasks/configure-pod-container/security-context/#set-the-security-context-for-a-container) configuration.
+* `containerSecurityContext.allowPrivilegeEscalation` - bool, default: `false`  
+
+  Control whether a process can gain more privileges than its parent process.
+* `containerSecurityContext.capabilities.drop` - list, default: `["ALL"]`  
+
+  A list of the Linux kernel capabilities that are dropped from every container. Valid values are listed at https://man7.org/linux/man-pages/man7/capabilities.7.html Ensure to remove the "CAP_" prefix which the kernel attaches to the names of permissions.
 * `shareProcessNamespace.coordinator` - bool, default: `false`
 * `shareProcessNamespace.worker` - bool, default: `false`
 * `service.type` - string, default: `"ClusterIP"`

charts/trino/values.yaml

@@ -267,6 +267,15 @@ securityContext:
   runAsUser: 1000
   runAsGroup: 1000
 
+# -- [Container security context](https://kubernetes.io/docs/tasks/configure-pod-container/security-context/#set-the-security-context-for-a-container) configuration.
+containerSecurityContext:
+  # -- Control whether a process can gain more privileges than its parent process.
+  allowPrivilegeEscalation: false  
+  capabilities:
+    # -- A list of the Linux kernel capabilities that are dropped from every container. Valid values are listed at https://man7.org/linux/man-pages/man7/capabilities.7.html Ensure to remove the "CAP_" prefix which the kernel attaches to the names of permissions.
+    drop:
+      - ALL
+
 shareProcessNamespace:
   coordinator: false
   worker: false