[identity_service] Implement account management operations

[barbu110]

Implement all the operations for account management:

• UpdateProfile: Updates the profile information of the given user account. Profile information refers to first name, last name and other such fields, but not email address or password
• UpdateEmail
• InitiatePasswordReset: Starts the password reset process for an existing user account by generating, securely storing and sending a password reset token to the email address registered on the account; this password reset token can be provided to the UpdatePassword operation to perform the actual password change
• UpdatePassword: Performs a change of the password associated with an existing user account while performing all the necessary validations (Note: this operation takes either the current password of the user account or a valid password reset token in order to allow updating the password).
• UpdateAccountState

[barbu110]

UpdateAccountState implemented in 8bb3653.