add mail entity and config
Merge branch 'HEAD' of https://github.com/AndreeaUrsulescu/issue-tracker.git

Conflicts:
	src/main/java/internship/issuetracker/entities/Comment.java
	src/main/java/internship/issuetracker/entities/Issue.java
	src/main/java/internship/issuetracker/entities/Label.java
	src/main/java/internship/issuetracker/service/IssueService.java
solve conflicts