Fix to Email Sending Issue with SparkPost

[mabumusa1]

Q	A
Branch?	3.0
Bug fix?	yes
New feature?	no
Deprecations?	no
BC breaks?	no
Automated tests included?	yes
Related user documentation PR URL
Related developer documentation PR URL
Issue(s) addressed	#8621

Description:
This issue happen when you use Sparkpost, Swift Mail throws an exception and the emails are not sent.

Steps to re-produce:

1. Select sparkpost
2. Send a campaign email or segment email and send
3. You will get the following error

mautic.ERROR: [MAIL ERROR] content.headers json dictionary value has type 'number' when expecting type 'string' Log data: !! content.headers json dictionary value has type 'number' when expecting type 'string' (code: 0) (send); victorcampuzano@XXXXXXXXXXXXXXX.com {"exception":"[object] (Swift_TransportException(code: 0): content.headers json dictionary value has type 'number' when expecting type 'string'\nLog data:\n!! content.headers json dictionary value has type 'number' when expecting type 'string' (code: 0) at

[codecov]

Codecov Report

Merging #9006 into 3.0 will increase coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff            @@
##                3.0    #9006   +/-   ##
=========================================
  Coverage     35.24%   35.24%           
- Complexity    27900    27907    +7     
=========================================
  Files          1731     1731           
  Lines         96443    96452    +9     
=========================================
+ Hits          33987    33995    +8     
- Misses        62456    62457    +1     

Impacted Files	Coverage Δ	Complexity Δ
...undle/Swiftmailer/Transport/SparkpostTransport.php	71.85% <0.00%> (ø)	84.00 <0.00> (ø)
app/bundles/PointBundle/Model/PointModel.php	24.26% <0.00%> (ø)	44.00% <0.00%> (+1.00%)
...pp/bundles/EmailBundle/Form/Type/EmailOpenType.php	0.00% <0.00%> (ø)	5.00% <0.00%> (ø%)
...dles/EmailBundle/EventListener/PointSubscriber.php	80.00% <0.00%> (+7.27%)	13.00% <0.00%> (+6.00%)

[mabumusa1]

@dennisameling may you please review this issue, it is blocking a lot of people who use sparkpost

[dennisameling]

@mabumusa1 Thanks, will test on Wednesday :)

[kuzmany]

@mabumusa1 Can you add title of this pull requests and description?

[mabumusa1]

@kuzmany changed the title and added description

[dennisameling]

Created a Sparkpost account to test this PR. If the 2nd reviewer needs my account to test, please reach out via Mautic Slack.

Can confirm the bug exists:

[2020-07-15 19:18:58] mautic.ERROR: [MAIL ERROR] content.headers json dictionary value has type 'number' when expecting type 'string' (send); <REDACTED> {"exception":"[object] (Swift_TransportException(code: 0): content.headers json dictionary value has type 'number' when expecting type 'string' at /var/www/html/app/bundles/EmailBundle/Swiftmailer/Transport/AbstractTokenArrayTransport.php:300)"} []

After applying this PR, it works as expected. Thanks @mabumusa1! 🚀

[RCheesley]

Confirm the bug before applying the PR:

[2020-07-19 20:51:46] mautic.ERROR: [MAIL ERROR] content.headers json dictionary value has type 'number' when expecting type 'string' (send); HenryLCatalano@einrot.com, ruth@cheesley.me.uk {"exception":"[object] (Swift_TransportException(code: 0): content.headers json dictionary value has type 'number' when expecting type 'string' at /Users/ruth.cheesley/Sites/local.mautic3/mautic/app/bundles/EmailBundle/Swiftmailer/Transport/AbstractTokenArrayTransport.php:300)"} []

Emails successfully sent when the PR is applied! 🎉