Allow projectId override in Firebase authentication

[femrtnz]

Hi All,

This is my first PR on spring-cloud. Please let me know if you have any questions or suggestions.

Fixes #2178, I'm enabling the project ID to be set on FirebaseAuthenticationProperties.java so you can use a different project ID

[codecov]

Codecov Report

Merging #2405 into master will decrease coverage by 0.02%.
The diff coverage is 62.50%.

@@             Coverage Diff              @@
##             master    #2405      +/-   ##
============================================
- Coverage     74.00%   73.97%   -0.03%     
- Complexity     2108     2109       +1     
============================================
  Files           263      263              
  Lines          7604     7609       +5     
  Branches        787      788       +1     
============================================
+ Hits           5627     5629       +2     
- Misses         1614     1616       +2     
- Partials        363      364       +1     

Flag	Coverage Δ	Complexity Δ
#integration	?	?
#unittests	73.97% <62.50%> (-0.03%)	2109.00 <3.00> (+1.00)	⬇️

Impacted Files	Coverage Δ	Complexity Δ
...ure/security/FirebaseAuthenticationProperties.java	50.00% <33.33%> (-10.00%)	3.00 <1.00> (+1.00)	⬇️
...urity/FirebaseAuthenticationAutoConfiguration.java	92.85% <80.00%> (-7.15%)	5.00 <2.00> (ø)

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[meltsufin]

Thanks for the contribution again, @femrtnz!