[Observability alerting] Save group information with dynamic mapping

[maryam-saeidi]

Summary

In this PoC, we are implementing saving group by information dynamically for the custom threshold rule. This consists of two parts:

1. Adding a dynamic field

// kibana.alert.grouping
[ALERT_GROUPING]: {
    type: 'object',
    dynamic: true,
    array: false,
    required: false,
  },

2. Adding a dynamic template

dynamicTemplates: [
      {
        strings_as_keywords: {
          path_match: 'kibana.alert.grouping.*',
          match_mapping_type: 'string',
          mapping: {
            type: 'keyword',
            ignore_above: 1024,
          },
        },
      },
    ],

The result of adding these mappings can be seen below:

Source 1	Source 2	Mapping

[elasticmachine]

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