Spike: Provide patchset for providing user changes to pkg via API

As a template user,
I want to consume a community template and provide my specific input,
so that I can reuse 95% of the awesome work that went into the template and still suit my needs

This piggy backs on the [pkg source identifier](https://github.com/influxdata/influxdb/issues/17998) work. The API consumer should be able to provide additional payload to identify changes to overwrite fields in the pkg.

the API would extend as follow:

```javascript
{
... existing fields,
// I don't like this name ;-(
patches: [
{
source: SOURCE_1,
resourcePkgName: PKG_NAME,
resourceKind: KIND,
changes: [
{
field: [charts, note],
indexes: [0, null],
value: VALUE
}
....
]
}
]
}
```

Start with the linked pkg source identifier work in issue 17998, then review how the API currently represents existing fields. Define how the proposed patches payload identifies a source, package, resource, fields, indexes, and replacement values. Done means the API contract for consuming a community template with user changes is agreed and documented.

Written by the indexing model from the issue text.