fix: server mounting [BREAKING CHANGE]

[chimurai]

Description

Fixes incorrect usage of originalUrl. Introduced in #18

Now you can modify the baseUrl; a feature which Express' app.use already provides..

// mount on "/users" and keep the "/users" base path
app.use('/user', createProxyMiddleware({'target': 'https://jsonplaceholder.typicode.com/users'}))


// mount on "/users" and change the "/users" base path
app.use('/user', createProxyMiddleware({'target': 'https://jsonplaceholder.typicode.com/customers'}))

Motivation and Context

• Add option to trim off baseUrl? #225 (comment)
• Add option to trim off baseUrl? #541
• refactor: use base node http types #723 (comment)
• RFC: drop mutation of IncomingMessage owned fields, write only to new, augmented fields expressjs/express#4854 (comment)

How has this been tested?

• Unit tests

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[coveralls]

Coverage decreased (-0.007%) to 98.788% when pulling 91c5715 on fix-originalUrl into 8a2e7a6 on v3.