support ephemeral storage request/limits

[elyesbenamor]

Closes #116

Add Ephemeral Storage Support

Description

This MR adds optional support for displaying ephemeral storage requests and limits in the kube-capacity CLI tool. This enhancement helps users monitor and analyze ephemeral storage allocation across their Kubernetes clusters, similar to how CPU and memory resources are currently tracked.

Features Added

• New -e or --ephemeral-storage flag to display ephemeral storage metrics
• Support for ephemeral storage in all output formats (table, JSON, YAML)
• Integration with existing -a (available) flag to show available ephemeral storage
• Container-level ephemeral storage metrics when using -c flag
• Pod-level ephemeral storage aggregation when using -p flag

Implementation Details

1. Added ShowEphemeralStorage boolean to the Options struct

2. Enhanced resource tracking structures:

   • Added ephemeral storage fields to nodeMetric, podMetric, and containerMetric
   • Updated tableLine struct for table output
   • Modified JSON/YAML output structures to include ephemeral storage

3. Updated formatters to handle ephemeral storage values:

   • Values are displayed in MiB format (consistent with memory)
   • Percentage calculations for requests and limits
   • Available storage calculations when using -a flag

Testing

• Tested with various pod configurations using ephemeral storage requests and limits
• Verified output formats (table, JSON, YAML) correctly display ephemeral storage metrics
• Confirmed compatibility with existing flags (-p, -c, -a)
• Validated percentage calculations and available storage display

Example Usage

# Show ephemeral storage in table format
kube-capacity -e

# Show ephemeral storage with pod details
kube-capacity -e -p

# Show available ephemeral storage
kube-capacity -e -a

# JSON output with container details
kube-capacity -e -c -o json

[elyesbenamor]

@robscott Here is a detailed MR that can be reviewed please