feat: add option to allow setting CURLOPT_INTERFACE

[ddelgrosso1]

This change is 

[scotthart]

Reviewable status: 0 of 4 files reviewed, 2 unresolved discussions

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google/cloud/internal/curl_options.h line 135 at r1 (raw file):

 * Sets the interface name to use as outgoing network interface.
 *
 * The default is to use whatever the TCP stack finds suitable.

Additionally, we may want to indicate that there's some formatting conventions available for the string per https://curl.se/libcurl/c/CURLOPT_INTERFACE.html

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google/cloud/internal/curl_options.h line 137 at r1 (raw file):

 * The default is to use whatever the TCP stack finds suitable.
 */
struct Interface {

I'm assuming we want users to set this directly, so let's move this from the "internal" curl_options.h to google/cloud/rest_options.h.

[ddelgrosso1]

Reviewable status: 0 of 5 files reviewed, 2 unresolved discussions (waiting on @scotthart)

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google/cloud/internal/curl_options.h line 135 at r1 (raw file):

Previously, scotthart (Scott Hart) wrote…

Additionally, we may want to indicate that there's some formatting conventions available for the string per https://curl.se/libcurl/c/CURLOPT_INTERFACE.html

Done.

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google/cloud/internal/curl_options.h line 137 at r1 (raw file):

Previously, scotthart (Scott Hart) wrote…

I'm assuming we want users to set this directly, so let's move this from the "internal" curl_options.h to google/cloud/rest_options.h.

Done.

[codecov]

Codecov Report

Attention: Patch coverage is 84.61538% with 2 lines in your changes missing coverage. Please review.

Project coverage is 92.90%. Comparing base (b25d354) to head (60230e7).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
google/cloud/internal/curl_impl.cc	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15044      +/-   ##
==========================================
- Coverage   92.90%   92.90%   -0.01%     
==========================================
  Files        2351     2351              
  Lines      210211   210224      +13     
==========================================
+ Hits       195297   195301       +4     
- Misses      14914    14923       +9     

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[scotthart]

Reviewed 1 of 4 files at r1, 4 of 4 files at r2, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @ddelgrosso1)

[ddelgrosso1]

/gcbrun