minor #16397 added the new Composer exclude-from-classmap option (annesosensio)
minor #16397 added the new Composer exclude-from-classmap option (annesosensio)

This PR was merged into the 2.3 branch.

Discussion
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added the new Composer exclude-from-classmap option

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
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65bef75 added the new Composer exclude-from-classmap option

symfony/security-bundle