Mongo breadcrumb: Summarize the length of long arrays

[johnnyshields]

Goal

In Mongo queries, it is very common to set a filter with "$in": [ some long array ] to avoid N+1 queries. Here's how this looks in the breadcrumb:

This is a problem because:

1. Its a ton of text
2. It's difficult to know how many members the array actually has.

Design

To fix this, in the Mongo filter field, an Array which (a) has more than 3 members and (b) does not contain nested Arrays or Hashes will be summarized as ["LENGTH=42"] (e.g. if it has 42 members)

Changeset

Only changes the Mongo breadcrumb functionality.

This also includes the changes from:

• https://github.com/bugsnag/bugsnag-ruby/pull/797 b/c I cannot commit from my Windows machine otherwise.
• https://github.com/bugsnag/bugsnag-ruby/pull/798 to avoid conflicts

Testing

Tested in RSpec and by TableCheck in production.

[clr182]

Hi @johnnyshields Thanks for raising this PR. We will be sure to take a look when priority allows us.