Add metrics with increment, gauge, and distribution support

[abogoyavlensky]

No description provided.

[abogoyavlensky]

Resolves #79

[sentry]

Bug: The attrs->params function calls reduce-kv on attrs without a nil check, which can cause a NullPointerException if metric functions are called with nil attributes.
_{Severity: HIGH}

Suggested Fix

Before calling reduce-kv on the attrs parameter within the attrs->params function, add a check to ensure attrs is not nil. If it is nil, return an empty collection to avoid the NullPointerException. A (when (map? attrs) ...) guard would be an effective way to handle this.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: src/sentry_clj/metrics.clj#L74-L80

Potential issue: The 4-arity versions of the `increment`, `gauge`, and `distribution`
functions pass their `attrs` argument directly to the `attrs->params` helper. This
helper function uses `reduce-kv` on `attrs` without first checking if it is `nil`.
Unlike `reduce`, `reduce-kv` throws a `NullPointerException` when called on a `nil`
collection. Therefore, if a user calls one of these metric functions with `nil` for the
`attrs` parameter, for example `(increment "metric" 1.0 :second nil)`, the application
will crash with a `NullPointerException`. This can happen in legitimate scenarios, such
as when building function calls dynamically.

[abogoyavlensky]

Looks like, reduce-kv on nil returns the initial value ([]) - it does not throw a NullPointerException. So, the fix might be not needed.